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, t
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TIN DEPOSITS
OF
THE WORLD,
Wll'H
A CHAPTER ON TIN SMELTING.
BY
SYDNEY FAWNS, F.G.S.,
Member of the Institution of Mining and Metallurgy ; Associate Member
of the Institution of Mechanical Engineers; Member of the
American Institute of Mining Engineers; Member
of the Royal Geological Society of
Cornwall.
SECOND EDITION.
THE MINING JOURNAL,
46, QUEEN VICTORIA STREET, E.C.
1907.
ao
/
fe'O
PREFACE.
THE literature of tin mining is at present in a scattered
condition. It is the object of the Author to produce
a collected account of the tin deposits and methods of tin
mining in various parts of the world which will be of some
practical value to the Tin Miner and Investor. It is
obviously impossible to visit personally all these deposits, and
the Author wishes to acknowledge the generous assistance
he has received from the Institlition of Mining and Metal-
lurgy, Institute of Civil Engineers, American Institute of
Mining Engineers, " The Mining Journal," " The Engineering
and Mining Journal," *' The Mineral Industry," Geological
Society of London, Royal Geological Society of Cornwall,
Geological Survey of United Kingdom, Geological Survey of
United States, Agents -General of Tasmania, New South
Wales, Queensland, and Western Australia, Geological Sur-
vey of New South Wales and Tasmania, Mr. Donald A.
MacAlister, R. Arthur Thomas, Alex. Gilfillan, H. Cutten,
J. H. Collins, Henry Louis, N. Samwell, L. Parry, Messrs.
Mercer Nicolaus & Co., Lake & Currie, Eraser & Chalmers,
and others.
The author wishes to thank the public and the critics for
the very favourable reception ot* the 1st Edition, and the
publishers for their kindness and generous assistance. In the
second edition the statistics and other matter has been brought
as far as possible up to date, and a chapter on Tin Smelting
has been added.
SYDNEY FAWNS.
62, London Wall,
London, E.C,
April, 1907.
211878
CONTENTS.
CHAPTER I. — The Common Forms op Stanniferous
Minerals and the Early History of Tin Mining.
Forms of Tin Ore — Native Tin — Stannite — Cassiterite — Franckite —
Cylindrit e — Ganfiedite — ^Teallit e — Stan oif erou a Argyrodite — Stokesite
— ^Crystallization — ^Wood Tin — Minerals occurring with Tin — ^Metallic
Tin — Deposition of Tin — Tin known from remote Antiquity — Ancient
Mining, Cornwall — Discovery near Marazion — ^Works of Agrioola and
Ecker — Sixteenth Century Mining — ^Mineralogia Cornubiensis — Tin
Out-put for several Centuries — ^Tin Production in Europe up to Six-
teenth Century ----1
CHAPTER IL— Description of Tin Deposits.
Fissure Deposits — Masses — Alluvial Deposits — Definition of Lodes
and Ore — Greological Features, Dolcoath Great Main Lode — Stanniferous
Veins of Cornwall, by Flett — Ages of Tin Veins and Granite, and Sizes
of Cross Veins and Lodes (Henwood) — Figures of Lodes (Foster) —
Dykes — ^Stock-works — Carbonas — Zones of Impregnation — Definition
of Alluvial Tin Ore — Sections, Malay Peninsula (Doyle) — Definition of
Alluvial Ore Depo«ts (CoUins) — Alluvial in Cornwall — Deep Leads of
Tasmania — Kampong Ling — Vegetable Creek, New South Wales — 9
CHAPTER III. — Alluvial Tin Deposits of the Malay
Peninsula.
Geographical Description — General Geology of Malay Tin Region —
Sections of Alluvial Deposits — Origin of Deposits — Description of
Kinta District, by R. A. F. Penrose, W. R. Rumbold— Geology of the
Taping District in State of Perak, by J. B. Scrivenor, Geologist to
the Federated Malay States — List of Mines in Perak - - - - 21
CHAPTER IV.— Alluvial Tin Deposits of Banoa,
BiLLiTON, SiAK, Sumatra, Siam, British Burma and
French Indo-China.
Geography of Banca and Biiliion — Geological Conditions — Banca
and its Tin Steam Works (P. Van Dust) — Method of working Section
of Alluvial Deposit — De Groot on Origin of the Tin Deposits — Billiton —
Sing Kep — Tin Deposits of Siak, Sumatra— Geology — Method of
working — Siam — Tin Mining Districts — Puket Island — Tin Deposits
of British Burma, described by Hughet, Alex. Gilfillan, and Cox — Stanni-
ferous Deposit j of FrentA. Indo-China - - - - - 38
b
CONTENTS.
Page
CHAPTER v.— Alluvial Tin Mining.
Forms of Sluicing — Description — Box Sluicing — Methods of working
— Mechanical Rake — Ground Sluicing — Method of working — Duty of
Water — Moving Power of Water — Alluvial Tin Mining, Malay Penin-
sula — Chinese method of working: — Hydraulic Sluicing Bruseh Mine,
Malay Peninsula . . . _ 54,
CHAPTER VI.— Tin Lode Deposits in the Malay
Peninsula.
Pahang Corporation — Description of Lodes on Property — F. J.
Stephens on Geology of District — Intrusive Rocks — Limestone — Slates
— Description of method of working Mine — Costs of Mining — Descrip-
tion ot Machinery— Out-put of Ore — Extract from F. M. S. Geologist
Report — Extracts from Report on Mineral Lodes, Lelania and Blanda
Mabok — Bundi Mine, Tringganu — Geology of Mine — Rocks and Min-
erals — Description of Ore Body — Costs of Labour — Sunghie Ayam,
Description of Ore Deposit — Chinese method of working — Stanniferous
Cements, Bukitt Ebie — Method of working — French Company at
Lahat — Output of Tin Ore from Lodes, Malay Peninsula - - 65-
CHAPTER VII.— Tin Deposits of New South Wales.
Geology of the Vegetable Creek Tin Mining Field— Stafinite — Cassit-
erite — Mode of Occurrence — Section Stanniferous AUuvials at Cope's
Creek — Tertiary Alluvial Deposits — Elsmore Valley Lead — Wellington
Valley Lead — Associated Minerals — Tin-bearing Lodes — Stock-works
Impregnations — Ottery Tin Lodes — Local Treatment of Ore — Burra-
Burra Deposits— Eur iowie Tin Lodes — Tingha and Inverell District,
Glen Innes Division 77
CHAPTER VIII.— Tin Deposits of Queensland.
Discovery of Tin — Herberton Tin Field — Geology of Ore Deposits —
Character of the Mining — The Vulcan Mine — Description of working
— Stannary Hill Mines and Tramway Company, Ltd. — Stanthorpe —
The Kangaroo Hill Mineral Field — Geology Waverley — Planet —
Kangaroo Hill and Douglas Tin Mining Companies — The Hidden
Valley Lodes — Summary from Government Annual Report, 1905 - 92;
CHAPTER IX.— Tin Deposits op Tasmania.
Description of Blue Tier District — Geology of the Tier — Description
of the Rocks — Dykes — Distribution and Grade of Ore — Anchor Tin
Mine — Description of Work on Mine — Dressing Sheds — Quantities —
Tin Deposits of the Ben Lomond District — Geology — List of Minerals
— Mount Rex Tin Mine — Description of Deposit — Working of Mine —
Tin Deposits in the Avoca District— rBrookstead Proprietary Company
— Roys Hill Tin Mine — Description of Briseis Tin Mine — Method of
working— Thureau's Deep Lead — Heemskirk District, West Coast - 9^
CONTENTS. Vll
Page
CHAPTER X. — Tin Deposits of Western Australia,
Northern Territory op South Australia, New Zea-
land AND Victoria.
Lode and Alluvial Tin Kimberley District — Description of Green
Bushes Tin Field — Alluvial Deposits — Tin-bearing Granite — Analysis
of Ore — Table of Exports — Description of Tin Deposits Northern Terri-
tory — Geology of District — Mount Shoobridge Tin Mine — Tin Deposits
of New Zealand — Tin Deposits of Victoria — Geology of Tin Deposits,
Mitta Mitta— Mount Wells Tin Field - - - - - 115
CHAPTER XL— Tin Deposits of Bolivia.
Description of Country — Geology — Tin-producing Districts of Oruro,
La Paz — Chorolque and Potofii — Huanuni Company System of Mining
— KlacoUo Tin Workings — Negro Pabellon Tin Mine — Sayaquiri Tin
Lode — Mines of Arecaija — Description of Method of working — Costs
of Mining and Transport — Lists of Mines — Chorolque Tin Mines and
Alluvial Deposits — Tin Production — Export Duties on Tin - - 122
CHAPTER XII.— Tin Deposits of Cornwall.
Early History of Mining — General Description of Cornish Mining —
Division of Cornish Lodes by Henwood — Geology of the Camborne
District, described at length by Donald A. MacAlister — Dolcoath Mine
— South Crofty Series — Levant Mine (St. Just) — Gurlyn Mine — Tin
Statistics for Cornwall 138
CHAPTER XIII.— Tin Deposits of Northern Nigeria,
Transvaal, Swazieland, Congo Free State, Japan,
Greenland, Finland, China, Korea and Siberia.
Occurrences of Tin Northern Nigeria — Province of Banchi, Badiko
District — Geology of District — Description of Deposits — Occurrence of
Native Tin — Analysis of Metal — Tin Deposit. Transvaal — Geographical
Description — Occurrence of Lodes — Cross Lodes — East Elvan — Alluvial
Tin — Tin Deposits of the Cape Colony — Swazieland Tin Field-
Description of Tin Field — Lodes — Alluvial — Tin Deposits Congo Free
State — Busanga Ridge — Lodes — Alluvial Deposit — Description of Tin
Deposits in Japan — Greenland — Finland — China — Korea — Siberia - 154
CHAPTER XIV. — Tin Deposits of Central Europe,
Spain, Portugal, France, Italy, Scotland, Ireland,
Mexico, United States of America and Alaska.
Mining in Altenberg District — Geological Features — Mining the
Stock-works — Mining in the Zinnwald — Ore Deposits of the Erzge-
birgs Saxony — Arnoyaseco Alluvial Deposits, Spain — Tin Deposits of
the Provinces of Salamanca, Orense, Ponteredra, and Almeria, Spain —
Deposits of Beiro — Minto — Tras-os-Montes, Portugal — Mining at Piriac
Vlll CONTENTS.
Page
CHAPTER XlY.—cont.
and LakiJleder, Brittany, France — Tin Deposits at Campaglia, Italy —
Description of Tin Deposits in Scotland, by Flett & Clough — Ireland,
by Louis — Tin Deposits of Durango and Teocaltiche — Geology of the
Potrillos District — Mining at Sain Alto, Mexico — Tin Deposits of the
United States of America — Tin Deposits California — Cajalco Hill,
Connecticut, Georgia, Idaho, Maine, Massachusetts, Missouri, Montana,
New Hampshire, South Dakoti, Texas Tin Deposits — Tin Deposits
of Alaska --------- 166
CHAI'TER XV.— Mount Bisohoff Tin Mine.
Situation of Mine — Description of Country — Geological Features —
Analysis, by Baron von Groddeck — Account of Deposit, by Von Fircks —
General Description of Geological Features — Queen Lode — White
Face — Brown Face — North Valley — Method of Mining — Description
of Machinery — Section of Hydraulic Jet Elevator — Working Costs - 184:
CHAPTER XVI.— The Dolooath Tin Mine.
Description of Mine — R. J. Frecheville — Account of the Great Main
Lode, Dolcoath — Country South of Main Lode, Camborne — 346-fathom
Level — Minerals in Lode — Country Rock — Changes in Killas — Output
of Mine — Crushing and Concentration at the Dolcoath Mine — Descrip-
tion of Stamps — Vanners — Treatment of Slimes — Cost of Treatment - 194
CHAPTER XVII. — Tin Crushing and Dressing Machinery.
Cornish Stamps— Calif ornian Stamps — Method of Erection — Pneu-
matic Stamps — Huntington Mill — Method at Mount BischofE and
Cornwall of handling the Crushed Ore — Frue Vanners — Wilfley Con-
centrator — Luhrig Vanner — Concave Buddie — Slime Table — Separation
of Tin Ore from Wolfram — Account of Machinery in Glitters Mine —
Fraser and Chalmers* Account of Experiments on Dolcoath Ore —
Relative Costs of working — Cost of Mining — Concentrators — Relative
Loss in Metal — Single Treatment without Classification and with
Classification — Double Treatment in two Sets of Vanners — Result of
some Experiments by Humbolt Company in Dolcoath Ore - - 204
CHAPTER XVIII.— Dredging for Tin.
General Description of Dredges — Spoon Dredge— Description of
Suction Dredge, with method of working — Hydraulic Dredge — Descrip-
tion of working — Specification of Machinery necessary — View of
Dredges at work, Cope's Creek — Bucket Dredge — Method of working —
Description of Dredge — Tailings Elevator— Specification of Dredge,
at Water Holes, Emmaville, N.S. Wales — Costs of working - - - 22
CONTENTS.
CHAPTER XIX.— Methods of Tin Assaying.
Page
Vanning Testa made by Richard Pearce — Assaying Method of
L. Parry — Cyanide A^say — German Assay Method — Wet Assay for Tin
— Gravimetric Assay by Electrolysis — Volumetric Estimation by Ferric
Chloride — Volumetric Estimation with Iodine in Acid Solution — ^Assay
of Tin Ore — George L. Mackenzie's Method of Determination of Tin in
Tailings and Slimes — Collins on the Assay of Tin and on the Solubility
of Cassiterite — New Methods of Separating Antimony and Tin - - 233
CHAPTER XX.— Statistics of Tin Production.
Discussion on Alluvial Output — Result of various Patented Processes
— Lode Mining Output — Output from Bolivia — Banca and Billiton—
Discussion on Output from newly -discovered Tin Fields — Tables of Tin
Production of the World up to 1906— Statistics of Tin— Tin Produc-
tion of Bolivia — Malay States — Tasmania — New South Wales — ^Western
Australia — Queensland — United Kingdom — Dutch East Indies —
Market Price of Tin for Twenty Years - - • - - 251
CHAPTER XXL— Tin Smelting.
Introduction — Description of Smelting Furnaces — Smelting Charges
— Tapping Furnace — Method of Buying Ore, Cornwall — Description of
Mr. BischofEs' Furnaces and Smelting Methods — Chinese Methods of
Tin Smelting — Description of Furnaces — Tin Smelting at Pulo Brani
— Arrangement of Works — Description of Furnace— Methods of Work-
ing — Description of Tin Smelting, Banca — Methods of Working - - 269
BIBLIOGRAPHY 296
INDEX - - - - - - - - 301
INDEX OF ILLUSTRATIONS.
■ 01
A
No. PAGE
1. Arrangement of Machinery on Bucket Dredge - - , - Facing 228
2. Anchor Tin Mine, Tasmania, Section of 101
B
3. Box Sluicing for Tin, New South Wales Facing 54
4. Bundi Tin Mine, Malay, Contact Deposit - 14
„ „ „ „ Section at Glen Reef 72
C
5. Carbonas at St. Ives Consols - -17
6. Chinese open Cast Working, Malay Peninsula - - - - Facing 36
7. Concave Buddie, Plan and Elevation ----- Facing 205
8. Cross Section of Lodes, Camborne, Cornwall - - - - - -140
9. „ „ „ Dolcoath Tin Mine, „ - - . Facing 194
D
10. Diagrammatic Sketch of Lodes, Camborne 142
11. Diagram showing Price of Black and White Tin 1905 and 1906 Facing 268
12. Dolcoath Sketch Plan, Main and South Lodes - - - - . 143
13. Double Tin Liquation Furnace Facing 288
E
14. Euriowie Tin Lode, New South Wales 90
F
15. Frue Vanner Shed, Dolcoath Tin Mine Faciyig 216
G
16. Geological Sketch Map of York Region 182
17. „ Map of Mount Bischoff District - . - - Facing 184
18. Greenbushes Tin Fields Water Supply Facing 118
19. Ground Sluicing for Tin, Tasmania Facing 56
H
20. Hanging Tramway, Dolcoath Tin Mine ----- Facing 198
21. Hydraulic Giant or Monitor 61
22* „ Sluicing, Brother's Home, No. 1, Tasmania - - Facing 58
23. „ „ Briseis Tin Mine Facing 62
I
24. Impregnation of Ore at East Wheal Lowell 17
25. ,. » » »> » » 17
XII INDEX OF ILLUSTRATIONS.
NO. ' M PAGE
26. Map of Australia showing Tin Deposits ... - Facing 92
27. „ „ Bqlivia „ ,, „ - - - - Facing 122
28. „ „ Cornwall and Devon „ „ Facing 138
29. „ „ Malay Peninsula „ . „ Facing 65
30. „ „ Tasmania „ ,,-.... Facing 99
31. Mining District of Gwennap, Cornwall - - • - - - 13
o
32. Overburden, Brother's Home, No. 1, Tasmania - - - Facing 110
33. Ore Dressing Plant, Gunnislake Clitters Tin Mine . - - Facing 214
F
34. Pedn an Drea, Longitudinal Section . , 145
35. Position of Tin Deposits, British Burma 50
36. Probable Section of Bukitt Bundi 70
R
37. Beverberatory Furnace, Pulo Brani, Singapore - - - Facing 276
38. „ M M „ „ Elevation - Facing 277
s.
39. Section of Alluvial Deep Lead 24
40. „ „ „ Ore Deposit, Banca 40
41. „ along drive in Bailey's Mine, N.S.W. 83
42. „ of Butler's Vein, Emmaville, N.S.W. 84
43. „ at Haley's Lease, Blue Tier 102
44. „ of Hydraulic Jet Elevator 189
45. „ „ the Kinta Valley - - - 27
46. „ „ Shallow Alluvial Deposit, Malay 24
47. „ „ Stanniferous AUuvials, Cope's Creek 78
48. „ ,, Stock Works at Zinnwald 16
49. ,, „ Surface Alluvial Deposit, Malay - - - - - - 24
50. „ from Vereinigt Zwitterfeld, Saxony 168
61. Slime Table, Plan and Elevation Facing 208
52. Smelting Furnace, Chinese 273
53. St. Day United Mines, Cornwall 145
54. Suction Dredge at Work, Cope's Creek, N.S.W. - - - Facing 226
55. Sketch Map of Kinta Valley Facing 27
T
56. Tin Assaying Apparatus, Parry 241
57. ,, „ „ McKenzie 244
58. „ Veins showing Cassiterite Pseudomorphs 14
59. „ „ „ Altered Killas 14
60. „ Sluicing, Kinta, iPferak Facing 28
61. Xyp^l Alluvial Mine, Malay Peninsula Facing 21
62. „ Bucket Dredge showing Tailings Elevator - - - Facing 230
V
63. View of Workings, Briseis Tin Mine Facing 112
W
64. WorkiU|i^ of Dolcoath Ore by Humboldt Company - - - - 221
OF THE
UNIVERSITY
OF
CHAPTER I.
THE COMMON FORMS OF STANNIFEROUS MINERALS
AND EARLY HISTORY OF TIN MINING.
Tin occurs in many forms as :
Native tin.
Stannite (tin pyrites, sulpburet of tin, tin sulphide).
Cassiterite (tin ore, black tin, tin oxide).
Franckeite Cyiindrite.
Caufieldite Teallite.
Stanniferous Argyrodite.
Stokes ite.
Native tin occurs in Bohemia, Bolivia, New South Wales, and
Northern Nigeria ; in Banca and Selangor small isolated specimens
have been found.
New South Wales, Aberfoil River. — Native tin in New South
Wales was first discovered in the washings from Aberfoil River about
15 miles from the town of Oban, N.S.W. Native tin exists in the
form of irregular grains or aggregations of such grains ; they are distinctly
crystalline from 0*1 to rarely over 1 mm. in size. When magnified
60 diameters they appear to be of an uneven surface, showing places
which are too indistinct for determining their form ; they are greyish
white and of metallic lustre. It was impossible to select enough of the
purest grains to make a quantitative analysis, or to determine their
specific gravity. A portion treated with hydrochloric acid dissolved
readily with disengagement of hydrogen, leaving fine scales of iridosmine
behind ; not a trace of auy other metal but tin could be found in the
solution.*
Northern Nigeria. — By far the most important discovery of
native tin has been made in the alluvial wash on the banks of the
Kogin River in the Badiko of the province of Banehi in Northern
Nigeria, the amount obtained being very large in comparison to any
other deposits of native tin. It is found in irregular grains, varying in
size from 0*1 mm. to about 3 mm. ; it is ductile, and when dissolved the
solution contained not a trace of any other mineral. There is apparently
no possibility of its having come from any native smelting furnace near.
This deposit has never been worked by natives, and the nearest native
* A. Liversidge, " Minerals of New South Wales," p. 77.
Z TIN DEPOSITS OF THE WORLD.
smeltiDg furnace is situated over 80 miles away. It is impossible as yet
to make definite statements as to its probable origin.
Stannite (tin pyrites, sulphuret of tio, or tin sulphide).— Commonly
massive or in grains. Colour, steel-grey to iron-black ; blackish streak.
Brittle. Hardness, 4 ; specific gravity, 4*3 to 4*6 ; composition :
sulphur, 30 ; tin, 27 ; copper, 30 ; iron, 13 to 100.
It is found at Zeehao, Mount Bischoff* and other places in
Tasmania ; also at Dolcoath and other mines in Cornwall ; Potosi and
Tatasi, Bolivia ; and in New South Wales. Stannite has a bronze-like
appearance and is frequently called bell metal ore in Cornwall. Being
generally associated with copper, it is nearly always sold as a copper
ore, the tin being disregarded.
* Crystallized Stannite (Bolivia). — Colour, iron black, with
bright metallic to sub-adamantine lustre, somewhat resembling black
blende mineral; is opaque streak, black and dull. Hardness, 3 J. Fracture,
sub-conchoidal. Specific gravity, 4 to 4'5. Chemical fcompositiou : —
I.
II.
Sn.
-
25-52
24-90
Fe.
-
10-95
10-90
Cu.
-
28-58
28-54
Sh.
-
3-54
3-88
Pb.
-
2-02
2-09
Ag.
-
•94
•82
Crystallized stannite
has a
remarkable
similarity to c
they are both scalenohedral-
■tretragonal.
copper pyrites ;
i Cassiterite (tin ore, black tin, or tin oxide). — Crystallizes in
the tetragonal system. The crystals occur in squares, prisms and
octahedrons, often in twins. The cleavage is indistinct. It also occurs
in a massive form and as grains. It varies in colour from brown-black
to yellow. The crystals have high admantine lustre. The »treak pale
grey to brownish. Hardness, 6 to 7. Specific gravity of the light
coloured, 6-4 to 6-85 ; of the black, 6^8 to 7-02.
Mr. J. H. Collins in his work on tin stones and tin capels, published
in 1888, writes as follows ; —
There are three distinct modifications of cassiterite.
(a) Crystallized (diamond tin, separable tin, rosin tin).
lli) Fibrous and radiated (wood tin, toad's eye tin, shoot tin),
(c) Pseudomorphous (after felspar, quartz, schorl).
\ The crystallization of cassiterite was worked out long ago
* Jour. Min. Soc, Vol. XIII., p. 54.
f Cassiterite is an original lode mineral ; it is insoluble, and consequently is not
acted on by the meteoric waters affecting the other minerals of the lodes. The
concentration is mechanical and solely the result of the washing away of the
sulphides w ibh which it is associated.
X Trans. Geo. Soc, VoJ. 2.
COMMON FORMS OF STANNIFEROUS MINERALS, ETC. 3
by Wm. Phillips, who calls attention to the fact that certain combinations
of forms are characteristic of certain deposits.
* The crystallization of cassiterite has been also written on by
F. Becke, 1877. Crystallized cassiterite is always more or less trans-
parent ; it is occasionally nearly colourless, but generally exhibits various
shades of brown from brownish-yellow to nearly black. Under the
microscope in thin sections it always exhibits a peculiar granular
appearance, somewhat like that observable in olivine. The purest
crystals are dark with polarized light and crossed prisms, but generally
even well-formed crystals exhibit bright sparkling granules due to
minute particulars of entangled quartz, t Cassiterite is distinctly
dichroic, but usually slightly so.
Wood Tin. — This is so called because of the resemblance of its^
fibrous radiated structure to that of exogenous wood ; it has been found
in both alluvial and lode deposits. J
At the Garth Mine, two miles west of Penzance, about 1827, wooil
tin in botryoidal masses and toad's eye tin occurred in great quantity,.,
together with ordinary crystallized tin stone, quartz, felspar, chlorite^-
and carbonate of iron.§
Wood tin is so nearly opaque and so brittle that it is difficult to get
a thin section for microscopic examination ; other forms of wood tin are
known as ''toad's eye" tin, "pea tin" and "shot tin." Pseudomor-^
phous crystals of cassiterite occur after felspar. The silicate of tin^
described by Mr. Garby is "perhaps a pseudomorph after quartz.
Cassiterite is usually associated with granitic rocks, porphyries,
gneiss, greisen and metamorphic rocks. In Mexico it occurs in
rhyolite and rhyolite-tuff, in Malay Peninsula and Japan in limestone,
in Greenland has been found associated with cryolite. The minerals
generally associated with tin ore are quartz, muscovite, mica, tourmaline,
fluorspar apatite, topaz, beryl, wolfram, molybdenite, mispickel, garnet,
biotite, iron oxide, chlorite, felspar, iron pyrites and talc.||
^Franckeite, a sulphur salt of tin, lead and antimony found at Poopo
Oruro Department, Bolivia. Occurs massive with imperfect radiated and
foliated structure. Cleavage perfect in one direction ; somewhat malle-
able. Hardness, 2'75. Specific gravity, 5'5 ; metallic lustre, colour,
blackish grey to opaque black ; having an average composition of : —
I.— Pbg, Sn:, Sb„ S,;
II.— 2PbSnS„ Pbg, Sb„ S^.
* Min. Mitt. 1877, p. 244.
f Analyses of crystals of cassiterite almost invariably reveal the presence of
small proportions of silica.
t TraDs. Koyal Geo. Soc, Cornwall, Vol. 1, p. 237.
I Carne, Trans. Boy. Soc. Corn., Vol. IV., p. 99-100.
II As the terms Cassiterite, Tin oxide. Tin ore and Black Tin are synonymous,
they are often used by the authors quoted as interchangeable terms.
ir A. W. Stelzner, Jour. Min. Soc, Vol, II., p. 114 (1893).
A 2
TIN DEPOSITS OP THE WORLD,
Analysis made by C. Winkler
as follows
—
8.
.
. 21-04
8b. -
.
- 10-51
8n. .
.
- 12-34
Pb. -
.
- 50-57
Fe. -
-
- 2-48
Zn. -
-
- i-2a
Gangue
-
•71
98-87
Cylindbite. — A sulphur salt of lead, tin, and antimony from
Poop6 Oruro Department, and Chocaya Potosi Department, Bolivia.
Massive forming, separating under pressure into distinct sheets or folia.
It is difficult to pulverize, like graphite. Hardness, 2-5 to 3. Specific
gravity, 5*42 ; metallic lustre ; colour, blackish lead-grey, streak, black.
Analysis : Sn., 26-37 ; S., 24-50 ; Sb., 8*73 ; Ph., 35*41 ; Ag., -62 ;
Fe., 3-0.
* Teallite (sulpho-stannite). — Colour, grey-black, metallic lustre.
.Soils paper like graphite ; occurs in flexible folia ; nearly square
outline ; perfect basal clevage. Hardness, 1 to 2 ; specific gravity, 6*36.
Orthorrhombic ; chemical composition, PbSnJ.
t Caufieldite (replaces the germanium). — The mineral occurs in
octahedro modified by dodecahedral planes ; brilliant metallic lustre ;
colour, black. Hardness, 2*50 to 3. Specific gravity, 6*27. Composi-
tion : Sn., 6-94 ; Ge., 1-82 ; S., 16-22 ; Ag., 74*10 ; Zn. and Fe., -21.
I Stanniferous Argtrodite (AuUagas, Bolivia). — Crystallizes in
simple octahedral crystals, usually with narrow dodecahedral planes ;
opaque, with dull iron-black colour streak black and shining. Fracture
is even, somewhat brittle. Specific gravity, 6-19. An analysis gave
the following result : —
Ag. - . - .
Ge. - . - -
Sn. - • . -
Fe.
99-68
§ Stokesite (silicate of tin). — Crystallographic characters : pris-
matic (bipyramidal) ; physical characters : cleavage perfect, conchoidal
* A. Frenzel, Jour. Min. Soc, Vol, 2, p. 125 (1893).
t T. Prior, Jour. Min. Soc, Vol. XIV.
t Jour. Min. Soc, Vol. XII.
§ Jour. Min. Soc, Vol. XIV.
COMMON FORMS OF STANNIFEROUS MINERALS, ETC. 5
fracture, brittle. Hardness, '6. Specific gravity, 3* 185 at 2*96.
Transparent ; colourless ; streak, white. Analysis : —
I. II.
SiO,
39-4
42-65
SnO, -
33-3
35-55
CuO
13-4
13-27
H,0
8-55 -
8-53
Fe,03 -
•7
—
Na,0 -
1-3
—
Loss
3-35 -
—
100-00 100-00
Metallic Tin is dimorphous, crystallizing in the forms of the
tetragonal and rhombic systems.* A bar of tin when bent emits a
characteristic " cry," which is caused by the individual crystals grinding
against one another on bending.
t The specific gravity of cast tin is 7*291, of rolled tin 7*299, of
electrically deposited tin from 7*143 to 7*178.
Tin is usually contaminated by iron, arsenic, antimony, lead, copper,
bismuth, tungsten, molybdenum and stannous oxide.
Tin is used in castings and for coating other metals, especially iron
and copper, also extensively employed as tinfoil.
I Tin dioxide obtained by a chemical process is employed on account
of its hardness in making a paste (putty of tin) for polishing hard
stones, sharpening fine cutting iostruments, and in preparation of
enamels.
The chlorides are used in the precipitation of colour used in dying
and calico printing. The bisulphide has a golden lustre and is used for
ornamental painting, paper-hanging and other purposes, under name
of bronze powder.
§ Tin occupies, in many respects, a unique position amongst the
various metals used in the arts, due not only to its specific properties,
but to an even greater extent to its mode of distribution and occurrence.
In the first place, it is the rarest of the common metals of commerce, and
is produced in markedly smaller quantities. Unlike most of these metals,
it is distributed sparingly throughout the world, occurring in workable
amounts at but few localities ; where it does occur, however, it is
generally, but not invariably, found in very important quantities.
Again, tin is the only common metal, except iron, the only true ore of
which consists of an oxide of the metal. All the other metals appear to
have been deposited originally as sulphides, their existence in the
oxidised state being due to the secondary action of atmospheric agencies
upon these sulphides. Hence the other metals are found as oxides near
* V. FouUon, Jahrb. der k. k. geolog. Reichsanstalt 1884, p. 367.
t Schnabel and Louis, *' Handbook of Metallurgy," Vol. 11, p. 375.
X Dana, " Manual of Mineralogy and Pttrograpby."
§ " The Production of Tin," Louis, published by 27be Mining Journal.
6 TIN DEPOSITS OF THE WORLD.
the outcrops only of their deposits, but as sulphides in depths, whilst tin
appears as an oxide wherever it has hitherto been found, even in the
deepest mines in which it has been met with, and at depths where
all other metals are known only as sulphides. It goes without saying
that sulphides present far greater difficulties than do oxides as regards
metallurgical treatment ; the former have usually to undergo a series of
more or less complex operations before they can be made to yield
up their metallic contents, whilst the latter need nothing more than
a simple reduction in an elementary form of furnace. Again, the
sulphides- of the other ordinary metals, when exposed to atmospheric
agencies, form more or less soluble compounds ; oxide of tin is notable for
its great chemical indifference and for its insolubility in those re-agents
that dissolve most other metallic compounds. Hence the degradation of
a mineral deposit containing any of the other metals is apt to be
accompanied by the removal in a state of solution of those other metals.
In the case of tin it will only lead to a concentration and purification of
the oxide. This is why oxide of tin (the tinstone or black tin of the
miner and cassiterite of the mineralogist) is found to so large an extent
in alluvial gravels, a mode of occurrence that it shares almost exclusively
amongst metallic minerals with those other chemically indifferent
substances, gold and platinum. When a mineral occurs in alluvial
jdeposits, it is far more easily got than when it has to be extracted by a
series of laborious operations from hard veins that extend vertically to
great depths, and which require considerable mining skill and advanced
engineering appliances for their exploitation.
Early History op Tin Mining.
* Tin has been known from remote antiquity, and as early as the
18th dynasty in Egypt bronzes containing 10 per cent, of tin were
used for tools and other purposes.
The alloy of copper and tin was much harder than copper, and was
consequently much used for making swords, spears, and hatchets.
These weapons were not forged, as at the present time, but were cast
in moulds and then hardened by grinding on stones.f
The components of the alloy varied in their proportions, as the
following analyses show : —
An ancient sword - - -
Copper
per cent.
- 89
Tin
per cent.
11
« 5> »» ." " "
An ancient weapon like a cutlass
- 85
- 90
15
101
A coin of Alexander the Great,
335 B.C. - - - -
- 86-72
13-14
♦ A. Cooper Key, "Ancient Mining," Trans. Inst, of Min. and Met., April 1896.
f *• Ure's Dictionary of Arts, Manufactures, and Mines."
J Hawkins, " Observations on Tin Trade of Ancients in Cornwall."
Copper
per cent.
85-15
Tin
per cent,
11-10
88-41
9-95
84-21
15-59
74-11
8-56
68-72
4-77
EARLY HISTORY OF TIN MINING.
A coin of Philippus V., 200 B.C.
„ ,, Atheus - - - -
„ „ Ptolemy TX., 70 b.c. -
., ,, Pompey, 53 b.c.
„ „ Atilia family, 45 b.c. -
,, „ Augustus and Agrippa, 30
B.C. 78-58 - 12-91
(The proportions of the other ingredients are omitted.)*
Nearly all the tin used by the ancients was procured by the
Phoenicians from the Cassiterides. A great deal of speculation has
been indulged in as to their position, and many authors .have been at
great pains to endeavour to prove that they were situated to the east of
Phoenicia in the neighbourhood of India. The great weight of
evidence and the testimony of the most learned archaeologists is, how-
ever, that they corresponded to the Scilly Isles and Channel Islands,
and, more particularly, Cornwall, which was in those dajs supposed to
be separated from the mainland. f
Two derivations have been suggested for this word Cassiterides but,
they may be independent or in reality one. " Kassiteros " is the Greek
word for tin ; but, possibly, this is the equivalent of the Hebrew word
" katseh " — fini>a, meaning the extremity of the earth, which the coasts
of Britain would have been to the ancients.
The commencement of the Phoenician working in these islands has
been assigned as about twelve centuries B.C. Diodorus Siculus, writing
just before the Christian era, and repeating what had been told by more
ancient chroniclers, giving an account of the work of the inhabitants of the
west of Britain, 8ays,J " They prepare the tin, very carefully working
the earth which produces it ; the ground is rocky, but has in it earthy
veins, the produce of which is brought down and melted, and purified.
Then, when they have cast it into the form of cubes, they carry it to a
certain island called Iktis. During the recess of the tide the interven-
ing space is left dry, and they carry over abundance of tin to this place
in their carts."
The Truro Museum contains a bronze casting of a bull about
2 inches in height which was found in Cornwall with many distinguish-
ing features of Assyrian bronzes. Moreover, a similar figure has been
discovered in Babylon. §
In 1849 Mr. Richard Edmonds discovered near Marazion a vessel
resting on charcoal ashes, charcoal and slag being also associated.
This was conjectured to be the remains of an ancient bronze furnace,
but Professor Hunt is of opinion that it was only used for domestic
* " Ure's Dictionary of Arts, Manufactures, and Mines."
t George Smith, " The Cassiterides."
J This translation is from Hunt's " British Mining."
§ Hunt, " British Mining."
8 TIN DEPOSITS OF THE WORLD.
purposes, on account of the " action of the molten tin upon a vessel
containing copper in its composition, which would be disastrous to the
vessel."*
The tin worked was probably of detrital origin.* The Phoenicians
jealously endeavoured to keep the tin trade to themselves, and for some
centuries they maintained the monopoly.
It seems uncertain how long the Phoenicians were masters of the
situation, but it was probably during a period of about 300 to 400
years. At the end of this time the whereabouts of the Tin Islands
were at last discovered by the other nations, and the Romans, Greeks,
and Gauls then came in to work the mines.
f It is certain that the first tin worked for many ages was derived
exclusively from alluvium. It is impossible to say when lode tin was
first discovered and worked.
The earliest German writers on these matters, Agricola and Ercker,
in the 16th century, describe the crushing and washing of tin-
bearing rocks as though this were a quite familiar operation, long
known and then already in a relatively high state of development.
During, at any rate, the 17th and 18th centuries, Cornwall seems
to have been the main source of the world's tin supply, its development
having been steadily progressive for many centuries. The average
annual production during —
Tons.
The 13th century is said to have been about - - 300
„ 14th 10 16th „ „ „ - 500
V 17th „ „ „ - 1,200
„ 18th ., „ „ . 2,600
* Hunt, " British Mining."
f " The Production of Tin," Louis, TJie Mining Jmirnal.
( 9 )
CHAPTER II.
DESCRIPTION OF TIN DEPOSITS.
The deposits in which tia occurs in economic form may be divided into
three divisions : (a) Fissure Deposits, (b) Masses, (c) AUuvial Deposits.
There are several sub-divisions under these headings, such as Lodes,
Dykes, Contact Deposits, Stock works, Carbonas, and Impregnations.
(a) Fissure Deposits^ Lodes.
The term " lode " as used by the practical miner includes the whole
of the workable band of mineralized country by the sides of the fissure
as well as the actual fissure filling. The great majority of this class of
ore deposits are of a later origin than the surrounding rocks.
The term ore is limited to metalliferous minerals of commercial
value still associated with the veiu-stone matrix in which they occur.
The contents of lodes result from one or more of the following
actions : —
(1) Infilling of a fissure by minerals derived from a distant source.
(2) Alteration and impregnation of the country rock in the vicinity
of a fissure by minerals derived from the fissure.
(3) Alteration and impregnation of a friction breccia (modification
of Nos. 1 and 2).
Many lodes are planes of faulting, and in consequence of comminu-
tion of the walls during movement of some sort, a great many of them
come under Class (3).
If a mineralized fissure in the lode area has all the peculiarities
of one of the ordinary lodes, such as direction of strike and the character
of the vein-stone, this vein is called a lode by the miners, whether
it contains payable ore or not.
Many lodes have been built up more or less intermittently by the
deposition from solution of a number of substances, some of which were
more or less chemically active than others, the result being that the lode
10 TIN DEPOSITS OF THE WORLD.
displays a variety of structures. Thus the simplest structure which
a lode can have is that which constantly figured in text-books — " the
Comby structure." There the lode is built up in layers parallel to the
walls of the lode, such layer representing a period of deposition and
possibly indicating repeated widening of the fissure, a feature charac-
teristic of tin lodes is the alteration of the country rock immediately
adjoining the fissure. This change is the result of metasomatism —
that is, the modification of the rock effected by the addition or taking
away of material. In many cases the rock adjoining the lodes is
worth breaking down for the cassiterite it contains.
Fissure lodes are supposed to have originated in the fissures or
dislocations which have been produced by various movements of the
earth's crust.* A fissure lode or its branches may at times coincide
with the dip of the strata, or the cleavage, but are subject to consider-
able variations in underlie ; in some districts the average inclination of
tin lodes has been accurately determined, as for instance in Cornwall,
where the average inclination has been given by Mr. Hen wood at 60^.
In all the various forms that tin deposits in situ assume, fissure
lodes or veins are the most important; they are the source of many
valuable ore deposits, and from their re;rularity and persistency, make
systematic and continuous working a profitable investment.
Lodes or veins occasionally meet without intersection or displace-
ment ; under this condition it is generally assumed that the lodes are of
the same geological age, and were contemporaneously filled with vein-
stone or ore.
In 1839 De la Beche pointed out that it is possible to fall into error
if we assume one lode to be older than another simply because the one
lode appears to be heaved by the other. The information concerning the
precise phenomena of the intersection of tin lodes is, however, extremely
meagre, and a very careful consideration of the facts governing each
case is necessary before any definite statement could be made regarding
the relative ages of the lodes.
Frequently Lodes are produced by the dislocation of ihe walls of
fissures, so that as a rule the walls have slid over one another, leaving
open and closed parts.*
The Dolcoath main lode in Cornwall is an excellent example of a
fissure deposit, and has been worked continuously for over a century.
It possesses some instructive and interesting geological features, and
several of the most important of these are given below.
This lode passes from kill as to granite without interruption. On
the surface of the lode a fine " gozzan " extended down for many
fathoms, which in places contained a good deal of tin ; the cnintry
rock changes noticeably with the lode matter. The killas is fairly soft
near the surface, generally becoming harder ss it approaches the
* Josiah Thomas (Jour. Eoy. Inst., Corn., 1868, Vol. III.) observed that the
widest part of the lode occurs principally where there is an abrupt change in the
strike, and constitutes a noticeable feature in the tin-bearing lodes of Cornwall.
DESCRIPTION OF TIN DEPOSITS. 11
granite, but it is always soft near the rich parts of the lode. Where
the granite is very hard the lode remains poorer in tin. The curious
alternations of killas and gi-anite through which this great lode cuts in
the upper levels has been noticed by many writers.
The exact depth at which lodes cease to be payable varies con-
siderably with the country rock, and the district in which they are
found. In Cornwall, it may be stated, tin lodes have remained payable
down to over 3,000 feet. Dolcoath is one of the examples of tin ore
remaining payable at great depths.
Tin lodes differ considerably in character. In no place have they
been so extensively worked and carefully examined as in Cornwall,
but the author is much impressed with the many features possessed in
common by the lodes examined by him in Tasmania, New South
Wales, and the Malay Peninsula, with those of Cornwall.
It is impossible here to discuss at length the origin of tin deposits
in situ, but a few main facts by recent observers may be cited.
In reference to Cornwall Dr. J. 8. Flett of the Gov. Geo. Sur-
vey in 1903 writes as follows on "The Stanniferous Veins of Corn-
wall " :—
"These modifications of granite, el van, and killas are the usual
accompaniments of the stanniferous veins, with which they have
undoubtedly a close genetic connection. In the veinstones quartz,
tourmaline, and a rather strongly polarising chlorite, are the commonest
minerals. Pyrites, arsenopyrite, chalcopyrite, fluorspar, and apatite
are rarely absent. The rocks which are worked as tin ores vary greatly
in character and in origin. Altered granites, killas, and true vein
deposits may all contain sufficient tinstone to enable them to be worked
for the metal. The true quartz lodes with cassiterite are very interest-
ing, as it is possible in some cases to show that they have a complex
history, as was pointed out by Mr. Collins.* The successive stages of
their formation can be made out with the help of the microscope, and
it can be shown that the fissures have been opened, filled with quartzose
vein stuff, which was then crushed up by movement of the walls, and
that these processes have been repeated three or four times in some of
the great lodes. Fragments of the first deposit lie scattered in a matrix
of the second, which in turn may be broken and cemented together by
a third infiltration.
" The tin veins are undoubtedly later than the granites and the
el vans, yet they show perfect cataclastic structures, which are singularly
rare in the igneous rocks. The later movements oE adjustment
seem to have taken advantage of the existence of the fissures, and
instead of interstitial granulitisation taking place in the intrusive
masses, these narrow veins of quartz, perhaps not entirely consoli-
dated at the time, have yielded to the stresses, and in so doing
have had their minerals shattered and ground down. This explains
the occasional occurrence of gneissic or granulitic types of el van and
* " Min. Mag.," VTol. IV., p. 20.
12 TIN DEPOSITS OF THE WORLD.
granite in Cornwall — a fact which has been brought to my notice
by Mr. J. B. Hill. Where the main granites are entirely massive,
some of the dykes or smaller sills are intensely sheared. Yet there
is reason to believe that they are later than the granite itself in some
cases."
In deciding the age of a lode it must not be assumed that
mineralization of the fissure commenced immediately after its formation,
movements operating for the production of a certain series of fissures
were undoubtedly followed by a period of mineralization which may
have occurred simultaneously or may have extended over very lengthy
periods of time.
Cross veins are wider in granite than in slate, and at great depths
than near the surface.
The mean width of cross-veins in granite is 4*9 feet.
„ „ „ slate is 3*5 „
„ „ at less than 600 feet deep is 4 „
„ „ at more „ „ 4*4 „
These veins alter considerably with the nature of the country through
which they run.
Out of 272 lodes recorded by Henwood as being divided by cross-
veins in different parts of Cornwall —
57 or 0*20 of the whole number were intersected but not heaved.
135 or 0*30 „ „ „ heaved towards the right
hand.
80 or 0*30 „ „ „ heaved towards the left hand.
181 or 0"67 ., „ „ heaved towards the greater
angle.
34 or 0*13 „ „ „ heaved towards the smaller
angle.
* The figures given by Mr. Henwood would probably differ con-
siderably if they were to include the workable portions of the lodes and
veins.
Dykes of quartz porphyry, known in Cornwall as elvan courses,
often carry tin oxide. These el vans are intimately associated geographi-
cally with the lodes ; that is to say, they occur in the principal mineral
areas, and like the lodes, occupy fissures which traverse alike both the
granite and killas. They may be regarded as an indication of the
presence of granite, since they are supposed to be derived from the same
magma ; the tin lodes themselves were formed during the later stages
of the consolidation of the granite, and generally they are of later age
than the elvans. They are generally large ; their bearing is tolerably
* J. H. Collins, "Origin and Development of Ore Deposits."
DESCRIPTION OF TIN DEPOSITS.
13
analogous to that of the principal lode? in each district. Since the
one operation followed so closely on the other, it is not surprising
to find that many of the ore bodies are actually found in or alongside
of the elvans.
Some very good examples of this class of tin deposit occur in the
St. Austell and other districts in Cornwall, and also on the north-east
coast of Tasmania, where these stanniferous dykes or elvans have been
extensively worked by the Anchor Tin Mine, Limited, and others.
Mining operations have revealed the presence of a greater number
of elvans both in the granite and kill as than can be found on the surface.
These elvans are often split up at a depth, and the general mode of
occurrence of the elvans suggests the infilling of fault fissures by
igneous matter.
The chief characteristic of these dykes or elvans in Tasmania is
their size, and, although the stanniferous value of these deposits is low,
still, with modern appliances and worked on a large scale, they possess
considerable economic importance.
The following figures illustrate some of the varied forms in which
tin lodes and dykes occur in Cornwall.
FIG. 1.— MAP OP PART OP THE MINING DISTRICT OP GWENNAP, CORNWALL (5.).
a rt, Granite : c c, Schistose rocks ; h 6, El van dykes ; «, ** Greenstone," vv^dd, two
interesting series of mineral veins. (Archibald Geikie.)
14
TIN DEPOSITS OF THE WORLD.
FlQ. 2. — ^Tin vein in Oomwall, with pgeudomorphs
of cassiterite after feldspar in the granite
country rock. (0. Le Neve Poster.)
FIG. 3. — ^Tin vein in Oomwall, showing
"capel" or altered "killas" country
rock. (0. Le Neve Foster.)
Contact Deposits are stanniferous lodes or veins which occur at
the planes of contact of dissimilar rocks. This class of deposit is
parallel to the stratification when it occurs between stratified rocks, but
is often found in irregular or rounded masses of a lenticular shape in
the spaces formed at the junction of two different rocks. Contact
Deposits generally occur at the junction of eruptive and stratified
rocks.
A very good example of this class of deposit occurs on the Bundi
Tin Mine in Tringganu on the east side of the Malay Peninsula.
The foot wall of this stanniferous ore-body is granite, while the
hanging wall consists of schists and slates, as will be seen from the
accompanying sketch.
Fig. 4.—^. Lode. -S.Granite. C. Schists and Slates.
(Jb) Masses^ Stockivorks, — In many tin fields bands or belts of
" Country rock " are found, which are traversed by numerous small
veins thinly lined or sprinkled throughout with small spots of metal-
liferous substances, the whole mass being of considerable value. An
ore mass of this nature is called by the Germans a " stock," and a
working upon such a mass a " stockwerk," or, as the term has been
adopted in England, " a stock work."
The origin of these stockworks is not always clear, but in the majority
of cases they are formed by the impregnation of a number of joints.
DESCRIPTION OF TIN DEPOSITS.
lo
cracks, or mere lines of rifting situated closely together. The country-
rock in the vicinity of these joints is generally altered to greisen and
other varieties of pneuraatolytically altered rocks to an extent entirely
obliterating the original character of the rock. The resulting mass may
have a homogenous appearance or may be banded in manner indicating
their origin.
Since the individual strings or nests of minerals are usually insig-
nificant, it is necessary in stockwork mining to remove the whole mass
of impregnated rock, or at any rate to treat the greater portion, in order
to concentrate and separate its valuable contents.
As the ores so distributed form a very small proportion of the rest
of the rock (generally about 10 tons of ore to the ton) a combination of
favourable circumstances is necessary to work them at a profit, and very
few will pay to mine except as open quarries.
Tin stockworks in Cornwall have been worked in ordinary " killas,*'
as also in granite and modifications, greisen, schorlomite and felspar
- porphyry (elvans).
In Tasmania stockworks are mined extensively in the Blue Tier
district, where they occur in a quarrz porphyry. (See Chap. IX.)
In the "Great Wheal Fortune " mine, Cornwall, a tin stockwork
in killas associated with a lode has been worked. The principal exca-
vation runs S.W. and is about 400 feet long and 50 feet Avide and 60 feet
deep. The average produce of the stuff stamped and treated is about
12 lbs. of tin to the ton. Tio stockworks in granite have been worked
which were unconnected with lodes, the granite in which the dissemi-
nated tin ore occurs being almost invariably altered into greisen,
schorlomite, or z witter.
Very large stockworks occur in the tin fields of Alton berg, Saxony.
These have been minutely described by Cotta, Dalmer and others.
According to Dr. Karl Dalmer* a belt of eruptive rocks breaks
through the Archssan sedimentary formations of the Erzgebirge in a
north-west line, along which are a series of fissures and important
faults. These eruptives may be classified as (a) quartz porphyry, (b)
granite-porphyry (younger than the former), and (c) a series of intru-
sive cones of granite (the most recent of the series). The tin deposits
are closely connected with the last named. They take the form of
" impregnation fissures," that is, fissures in the immediate neighbour-
hood of which, whether filled or empty, the country rock is changed
into a greisen impregnated with tin-stones, the width of the zone so
altered varying from a few inches to some yards. These impregnation
fissures are closely associated with the granite masses and the rocks in
contact with them. In the granite cones they are generally confined
to the boundaries thereof with the older porphyry, so that an outer ore-
bearing capping may be distinguished from the inner unaltered poor or
barren rock which succeeds it in depth. This phenomenon is well
* " Der Alternerz-Graupener Zimmerzlagerstatten District," Zeitsch. f. prakt.
G30l. 1894, p. 313.
16 TIN DEPOSITS OF THE WORLD.
marked at Altenberg, where a granite cone breaks through the granite
porphyry. The upper part of this cone is so completely traversed in
every direction by a close network of impregnation fissures that the
entire mass, except for some residual portions, has been altered to a
stockwork (Zwitter-gestein) of ore bearing greisen, which extends to a
depth of some 230 metres below the summit of the eruptive cone, at
which point the undecomposed granite, containing but a few narrow
belts of impregnations, makes its appearance.
Lakl
PIG. 5.— VERTICAL SECTION THROUGH TIN STOCKWORK AT ZlNNWALD, AFTER DALMBR.
A. Granite shaded portion shows limit of tin-bearing rock. B. Qnartz Porphyry.
C. Zone of impregnation.
* Carbonas are a somewhat similar class of deposit as stock works.
They may occur as either isolated ore bodies, or associated with a
deposit of a well-defined character. W. J. Henwood, in " Trans. Royal
Geol. Society of Cornwall," quotes the example of the St. Ives Con-
solidated Mine, where the carbona joined the Standard lode at a depth of
468 feet ; at this point it was only 5 inches square, but widened out to
60 feet, and was worked for 720 feet in length. This deposit was
enclosed in both sides by granite, and consisted of quartz, felspar,
schorl and oxide of tin, the chief characteristic being the gradual tran-
sition from granite to the carbona.
A section of this deposit, by H. C. Salmon, taken from "The
Mining and Smelting Magazine.'* (See Fig. 6.)
Impregnations occur as very irregular tin deposits, in conjunction
with lodes and generally associated with granite. They have no defi-
nite bedding planes, and are termed by the miner lode matter, and it
seems better (except for purpose of classification) for the geologist to
give way and suit his definition to the wants of the miner, as it is too
much to expect the miner to give up a term consecrated by universal
usage, because geologists have in the past made the mistake of suppos-
ing all lodes to have been formed on the same plan.
The Figs. 7 and 8 give an idea of a common form of a Zone of
Impregnation.
* Collins, *' Origin and Development of Ore Deposits.*'
DESCRIPTION OF TIN DEPOSITS.
IT
FIG. 6.— 0ARB0NA8 AT ST. IVES CONSOLS.
A. Williams* lode. B. Kemp's lode. C. Great Cbrbona. D. Daniels* lode.
£. Standard lode.
FlO. 7. — Impregnation of tin ore at East
Wheal Lovell, Cornwall. (C. Le Neve
Foster.)
FlO. 8.— Impregnation of tin ore at East
Wheal Lovell, Cornwall. (0. Le Nevfr
Foster.)
l8 TIN DEPOSITS OP THE WORLD.
(c) Alluvial Tin Ore Deposits have beea derived from the disinteg-
ration and denudation of older mineral deposits. In most cases the
material has been carried and re-deposited by the action of water,
often at considerable distances from their source. Some of these allu-
vial deposits are of great geological age, the alluvial tin ore deposit
near Avoca, Tasmania, being of post-carboniferous age (see Chapter II.),
but the majority of such deposits belong to the late Tertiary periods.
The general law which seems to govern these deposits would
appear to be that the relation of the depth of the overburden to the
depth of wash is in the ratio of about one to four.
* The following are five sections of alluvial tin leads from the Kuita
district, Malay Peninsula, which average about 4 feet of overburden to
1 foot of wash with ore : —
I. ft. in.
Vegetable mould - - - - - 1 3
Loam 10
Sand 4
Bluish clay 36
Darkish clay 3 9
Stratum with ore 6
II.
Mould soil - - - -
Clay varying dark yellow to pale grey -
Light gravelly drift - - - .
Stratum with ore - - - .
III.
Mould soil - - - -
Sand varying from white to brown
Dark grey sand - - - - .
Stratum with ore - - - .
IV.
Red loam
Sand drift
Whitish grey clay - - - .
Stratum of ore - - - -
19 6
24
18
28
Red earthy loam 5
Whitish grey clay - - - - - 3 6
Drift sand 8 6
Stratum of ore 80
25~0
These will average about 4 to 1.
* P. Doyle, Vol. XXXV., » Jour. Geo. Society."
DESCRIPTION OF TIN DEPOSITS. 19
Mr. J. H. Collins gives the following definition of alluvial ore
deposits : — " All clastic rocks, such as conglomerates and sandstones,
and even some clays, may be regarded as detrital deposits, whatever
their geological age. But the term is by custom restricted to
the but little consolidated sands and gravels of the later geological
periods. Such beds are found to contain distributed particles of ore-
matter, apparently derived from pre-existing rocks ; and when these
occur in workable quantities, or nearly so, the beds themselves may be
classed as detrital ore deposits."
There is very little alluvial tin ore remaining in Cornwall. Geolo-
gically there are two varieties :—
(a) * As a constituent of river gravel or sea beaches now in process
of formation the tin ore referred to is generally in very small particles,
often angular and sub-angular.
(b) The elevated stanniferous gravels such as those of the " Blue
Pool " in Crowan referred to by Mr. Zyack.t
There is distinct evidence that in some in«tances at least very con-
siderable thicknesses of overburden resting upon the tin gravels have
been accumulated within comparatively recent periods.
The actual proportion of tin oxide present in stanniferous gravels
is very small, but represents a considerable amount of denuda-
tion.
Frequently the deep alluvial deposits occupy the bed of an ancient
river flowing through valleys, which have been subsequently filled by
the outpouring of volcanic matter. A good example of this is the
Deep Lead worked by the " Briseis " and " Brothers Home " Mines in
Tasmania, which was undoubtedly at one time the bed of the old
Ringarooma River. The overburden has an averatre thickness of over
100 feet, the present surface being formed by an immense flow of
basalt, which is fully 80 feet in thickness in parts. These ancient
valleys were eroded at a period when the relative positions of the land
and sea were entirely different, as they are often much below the
present sea level. As evidence of this, the author would instance
the deep alluvial Tin Lead at St. Helen's, on the east coast of
Tasmania, where the bottom of the lead is over 100 feet below sea
level.
In the Malay Peninsula, at Kampong Ling, tin ore was worked
on the sea beach, the sand being washed on the spot in little wooden
troughs about 7 feet long by sea water, but the ore won was too poor to
pay expenses.
Alluvial tin ore occurs in nearly every part of the Malay Peninsula
for a distance of 900 miles, the chief district being Kinta, Perak.
The main features of interest in that locality are reproduced in nearly
every large area of alluvial tin ore. Much of the alluvium contains
the cassiterite in particles and fragments of varying size, sometimes
scattered from top to bottom in comparatively uniform quantities, and
* Collins, '* Origin and Development of Ore Deposits," p. 184.
t *< Trans. Roy. Geo. Soc. Cor." IX., p. 177.
B 2
20 TIN DEPOSITS OF THE WORLD.
in other cases in layers separated by barren ground, and often richest
near the bed-rock. (But in the author's experience it is a commoa
mistake to imagine the richest ore must necessarily be on the bottom.)
The overburden varies from 10 to 40 feet, and the best ground
occurs immediately at the foot of the mountains. Higher up it is
often richer, but of small extent, while further away it is thicker but
of lower grade.
The ordinary tin-bearing beds vary from 1 to 30 feet in thickness,,
though sometimes they reach over 100 feet.
In one instance the tin-bearing formations extend from the surface
down to a depth of from 5 to 50 feet, without any barren overburden..
In another instance large open pits in the alluvium of the river valley
show tin-bearing strata, varying from 2 to 10 feet in thickness, with
a barren overburden of 40 feet in thickness. In another instance the
overburden is from 30 to 40 feet in thickness, and the tin-bearing
ground below has penetrated 140 feet vertically without reaching the
bottom. In the mountains near its source the ore is angular and in
comparatively large fragments, sometimes from an inch to a foot or
more in diameter. Further down the hill it becomes more and more
rounded and finer in grain.
At Vegetable Creek, New South Wales, the tin gravels are derived
from masses of granite which are penetrated by numerous small tin.
veins, but no tin-lodes or stockworks have as yet been profitably
exploited. The width of the channel deposits of Vegetable Creek
vary from 5 to 15 chains or from 330 to 990 feet, the richest portion
being from 1 to 5 chains wide. The average thickness of tho
stanniferous gravels is about 2 J feet, yielding about 20 lbs. to the cubic
yard or 0*8 per cent.
The older depositions of alluvial tin ore appear to be mostly of
Miocene origin, and undoubtedly very considerable changes have taken
place in this class of deposits. To illustrate the important changes
that occur in the deeper gravels subsequent to their deposition in
silicification, there are in the British Museum,* as well as in the
Museum of the Royal Geological Society of Cornwall, fragments of
antlers containing tin oxide, which appears to be pseudomorphous after
the organic tissues. Many of the fragments are said to have been
found in the Streamworks of the Pentewan and Carnon valleys. Some
of the specimens preserved in the British Museum appear to contain a
large quantity of tin. In many parts the original structure seems to-
have disappeared and to be entirely reproduced as cassiterite.
* Phillips and Xjouis " A Treatise of Ore Deposits," p. 33.
OF THE
iVERSJTY Ji
or
( 21 )
CHAPTER III.
ALLUVIAL TIN DEPOSITS OF THE MALAY
PENINSULA.
The deposits of alluvial tin ore have in the past history of tin mining,
and still continue in the present, to supply by far the greater propor-
tion of all the tin raised in the world. The chief sources of supply are
situated in the Malay Peninsula, BaDca, and Billiton.
These deposits may be said to extend from about the 12 degrees
N. lat. to Banca and Billiton in the south.
The Malay Peninsula is the south-eastern extremity of the con-
tinent of Asia, extending from about latitude 14° N., in a southerly
and south-easterly direction to about latitude 1° 20' N., and consisting
of a narrow strip of land about 900 miles in length and from less than
50 miles to over 150 miles in width. The northern part of the
peninsula belongs to Siam, though the British possessions of Burmah
include some of the north-western part. The central and southern
part of the peninsula is comprised mostly in the native States of
Perak, Pahang, Selangor, Negri Sembilan and Johor, ruled by inde-
pendent Sultans, but under British protection, and now combined under
the name of the Federated Malay States.
* The Federated Malay States at present comprise most of the tin
regions worked on the peninsula, and tin deposits occur in greater or
less quantities from the State of Johor, in the southern extremity of
the peninsula, northward to the limit of the State of Perak on the
Siamese border, a distance of some 350 miles. To the north of this
limit, in Siam, the tin deposits have not been much explored, and no
very prominent mines have been opened as yet. By far the larger
part of the tin of the peninsula is mined in the States of Perak and
Selangor, while very little has been mined in Johor, and the production
of Pahang and Negri Sembilan is small. Perak supplies considerably
over half of the tin of the peninsula, and the Kinta District is at pre-
sent the most important tin locality in that state. In Selangor the
* The Federated Malay States of the Malay Peninsula consist of the four states
of Perak, Selangor, Negri Sembilan, and Pahang. They adjoin each other ; the
three first-named states lie on the western side of the chain of mountains which
forms the backbone of the peninsula, while Pahang is situated on the eastern side
of the range, extending to th^^ shores of th^ China Sea. The total area of the four
states is estimated at about 27,000 square miles.
22 TIN DEPOSITS OP THE WORLD.
most important mining centre is Kuala Lumpur, and the production of
this region is second only to that of the Kinta District. Besides the
places already mentioned many other smaller tin districts exist, and in
fact most all of the numerous small native towns on the west slope of
the peninsula are largely dependent on the tin industry.
General Geology op the Malay Tin Regions. — The Malay
Peninsula consists of a central axis of rugged mountains with occa-
sional subordinated parallel or diverging axes and isolated peaks. The
whole region is covered by a jungle of tropical vegetation so dense that
the roads and trails have to be hewn through it with an axe. In the
tin regions the main range is composed of granite rocks, occasionally
intersected by felspathic and other dykes, while in places are found
gneissic and schistose rocks with occasional areas of a white highly
crystalline limestone. The granite is mostly of a grey colour, and is
composed of quartz, felspar and biotite, or hornblende, or both. Occa-
sionally strata of a fine-grained friable sandstone occur on the lower
slopes of the mountains. The granitic rocks and limestone, however,
are the formations most commonly seen in the few places where any
rocks appear through the soil.
It is in the mountain valleys and the extensive lowland near the
coast that the large areas of alluvium are found ; the stanniferous por-
tion varies in thickness from a few inches to 16 feet, and generally in
relation to the overburden, which also varies from about 1 foot to
80 feet. There are three distinct forms, which are given below :
1. Surface alluvial.
2. Shallow alluvial.
3. Alluvial deep leads.
(1) Surface Alluvial, — Top soil carrying payable tin right down
from the grass roots. This class of deposit seldom much exceeds
15 feet in depth, and may be ternied " surface alluvial."
(2) Shallow Alluvial. — Stanniferous washdirt, usually 10 to
20 feet deep, lying under 15 to 20 feet of overburden. This is the
most usual form of deposit met with in Perak, especially in Kinta, and
will be referred to as "shallow alluvial." It will sometimes happen
that there are two layers of washdirt, known respectively as " karang
gantong " (hanging washdirt) and "karang betul " (true washdirt)
with 10 to 20 feet of barren soil or gravel intervening, before the
" kong " or bed-rock is reached. It is hardly correct, as has been
stated by some, to say that this upper layer is generally unprofitable.
In Perak, at least, it often happens that it is quite as payable as the
lower layer, and occasionally even more so ; indeed, there appears to
be no general rule on the subject. This class of deposit is naturally
more expensive to work than the "shallow alluvial" previously de-
scribed, as the overburden has to be stripped before the payable part
can be attacked.
(3) Deep Leads, — " Deep leads " with 30 to 50 feet of overburden^
and occasionally even more. Here, either open cast workings on a
ALLUVIAL TIN DEPOSITS OF THE MALAY PENINSULA. 23
considerably larger scale must be carried out, or shafts sunk, and the
deposit worked on a regular system of underground mining. However
correct it may have been a few years ago to state that this form of
deposit was but little known in the Straits, it can scarcely be said to
apply at the present time in view of later developments. Indeed,
to-day many of the largest Chinese workings in Perak and Selangor
are on " deep leads," and some have been carried as deep as 400 feet,
* Value of Tin Alluvial. — To give some idea of how rich some of
the Perak tin gravels have been, a list of twelve samples, taken about
two years ago by the State Geologist from Chinese mines in the neigh-
bourhood of Taiping, is appended : —
Lb. of black tin
No. per cub. yd.
1 77-375
2 22-793
3 20-220
4 18-719
5 17-899
6 15-864
7 15-327
8 15-044
9 12-894
10 - 10-299
11 10-179
12 5-455
Average of 11 samples = 14-972 lb. per cub. yd. The first sample,
being of quite exceptional richness, is omitted in taking the average.
With metallic tin at $32-00 per pikul (at the mean rate of exchange
taken) = £59 8*. 4c?. per ton, and assuming the produce to be 70
per cent., the mean value of the 11 samples works out at $2*51
(5*. 6Jc?.) per cub. yd. The average value of alluvial throughout
the state is nothing like so high as this at the present time ; 2 to 4
katis (2-6 to 5-2 lb.), equivalent on the same basis to 64c. to $1-28
(1*. 5d. to 2s. 10c?.) per cub. yd., would be a gooa Ueai nearer the
mark. Perhaps it would not be far out to say that 1 kati (1*3 lb.) of
black tin ( = 32 c, or 8^^^.) to the cub. yd. about represents the limit
of payable washdirt with an average alluvial mine in Perak.
The rise in the price of metallic tin from about £60 per ton in 1897,
when Mr. Owen compiled these figures, to the present price of about
£190 per ton, causes considerable difference in values.
Thus 1 kati (1-3 lb.) of black tin would now be worth 50c. (or 1*. 4c?.)
to the cubic yard.
This rise naturally widens the area of payable operations, and there
are large areas of poor ground which can now be worked at a profit. But
the profits of the Chinese mine proprietor, employing much labour, have
not increased as rapidly as might be supposed from the fluctuations in
* Owen. F., " Trans. Inst, of Min. and Met.," Vol. VI., 17th Nov. 1897.
24
TIN DEPO&ITS OP THE WORLD.
tin quotations recently. The cause of this has been in the standardi-
zation of the dollar at 2s. 4:d. (56 cents), after fluctuations from
neighbourhood of Is, 9d. to 1*. lie?. (42 to 46 cents). Yet the wages
of coolies have seen no diminution. Nearly all the expenses incurred
by the mine-owners, save the importers of coal and machinery, have
advanced proportionately. During the three years, 1902, 1903, and
1904, the average valuation was $80 per picul (133 lbs.), and had the
B^d Fig.lO Fig.U
* 4 - ■■ ^
'O "-* 9-
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i
8
Fig. 9.— Section op Surface alluvial Deposit,
A, Surface. B. Sandy and clayey ; stanniferous washdirt. C. Bed-rock— granite or limestone.
Fig. 10.— Section op Shallow Alluvial deposit.
A. Surface. B. Overburden— sandy and clayey. C. Stanniferous washdirt (karang ^antong)
or hanging washdirt. D. Barren gravel. E. Bich stanniferous washdirt (karang betul or true
washdirt) containing crystalline quartz-felspar, etc. F. Bed-rock — granite or limestone.
FIG. 11.— Section op Alluvial Deep-lead
A. Overburden— clayey and sandy. B. Stanniferous washdirt (25-50 catties of tin per cubic yard).
C. Stanniferous washdirt (25-70 catties of tin per cubic yard). SKghtly mineralized (pyrites).
ALLUVFAL TIN DEPOSITS OP THE MALAY PENINSULA. 25
dollar been 2s, 4d, (56 cents), would have been equivalent to £160
($800) per ton.
The three typical sections shown here were prepared for the author
by Mr. N. Samwell, who has had considerable experience in working
the Malay alluvial deposits.
Fig. 11 is taken through the Ipoh VaJley and Perak ; no bed-
rock was reached at a depth of 200 feet — the bed rock reached in the
shallower mines here is Limestone. Some deep leads in Malay have
been worked down to 400 feet before reaching bed-rock.
The exact origin of these deposits is still a matter of controversy,
but when the geological survey, now in progress, of the Federated
Malay States is finished very valuable data will be furnished. In
general they have doubtless been derived from the denudation of the
granities, and other tin-bearing matrices, some of which are comparable
with the stockworks of Saxony, Cornwall, and elsewhere.
This view has received considerable support from the discovery in
some deep workings in Kuchai, in Selangor,* of narrow veins of
cassiterite traversing a formation consisting of quartz with a little
felspar, capped with kaolin, produced by its decomposition in situ^ and
containing much disseminated cassiterite. It is possible that the
stanniferous portion of the granite formed a shell on the unaltered
central portion ; the tin being developed at the junction of the granite
with the stratified rocks on its flanks, as in the case of the Erzgebirge
in Germany.
The author has had the opportunity of examining large bodies of
alluvial wash in close proximity to their known source in the province
of Kemamau, in the north-east of the Peninsula, at the Buudi and
Sughie Ayam Mines, Large quantities of alluvial tin were recovered
from the karang or stanniferous gravels on the eastern side of the
lodes in this district ; the strike of the lodes being practically north
and south in both cases. The topographical features of the country
are a continuous slope of the ground towards the east, and a continuous
rise of the ground towards the west. In neither case was any payable
alluvial found on the western side of the lode ; the lodes occurring on
the contact of the slate and granite country. The debris showed both
boulders of granite and slate. In some of the old alluvial workings at
Sughie Ayam a number of both large and small boulders, rich in finely
disseminated cassiterite, also of quartz with nodules of cassiterite,
have been stacked by the Chinese workers. These boulders show very
slight signs of denudation, and closely resemble the lode matrices which
are at present being worked a short distance away from where they
were found. At a greater distance the wash has been covered to a
depth of some 10 to 20 feet with overburden, consisting mostly of clay
with a loam top.
In the flats the wash shows to a greater extent the rounding action
of water, there being few large boulders ; the major portion consisting
* Reports on the Federated Malay States for 1894.
26 TIN DEPOSITS OF THE WORLD.
of granite, slate, and quartz pebbles with the cassiterite in small
crystals.
There can be no doubt in both of these instances where tin
originally came from, as the lodes and the surrounding country show
evidences of considerable denudation.
M. de la Croix, writing on the origin of alluvial tin ore in Perak,
Malay Peninsula, says : — " All the granites are traversed by veins of
quartz, which course through them in every direction, and which are
the veritable deposits (gites) of the tin."
TheRev.Tennison Wood, disagreeing with the last authority and with
the generally entertained belief of the uninitiated, does not think that
the alluvial tin has been derived from lodes, or that such will be found.
Elsewhere, however, he states, " nevertheless, in Northern Perak there
are tin veins or true lodes," the true matrix of the tin being, in his
opinion, " in the granite at its junction with the clays, where it has
been disseminated abundantly in fine grains." " The whole of the
granite of the Peninsula contains tin," says this author, "but it is at
the junction of this granite with the palaeozoic clays that the richest
deposits of tin have taken place," and he suggests that one should " sink
through the clay strata," where they have not been denuded, to tap
these " second bottoms," as he calls them. Mr. Wood's theory is
advanced, he confesses with «ome diffidence, to account for his supposed
form of deposits. " Sublimation of the metal from its plutonic magma,
its oxidation and condensation on the edges of the clay strata where
metamorphism was not complete." * From his own observations the
writer is of opinion that this occurrence of cassiterite, which must be
of prodigious extent, and yet is so strangely unrecognisable, is chiefly
in the form of an integral constituent of some varieties of the granite,
such as " greisen," in certain zones ; and also in the shape of minute
veinlets with quartz disseminated through such zones ; and, though
occasionally irregular, shaped mannes of considerable size of more or
less pure cassiterite, generally associated with limonite, are found out-
cropping in the bed-rock bottoms of alluvial workings, indicating the
concurrent existence of some form of massive irregular deposits ; these
latter are but exceptional segregations of minor importance to the main
form of occurrence.
The following description of the Kinta District, by R. A. F. Pen-
rose, jun., appeared in "Engineering and Mining Journal," June 20th,
1903 :—
" The Kinta District in Perak has no definite boundaries, but the
name is a general term applied to an area in the southern part of the
State of Perak, in the valley of the Kinta River, comprising a more or
less enclosed valley about forty miles in length in a north and south
direction, about thirty miles in width at its south end, and about five
miles at its north end. To the east is the high granitic range forming
the backbone of the peninsula, and rising in some places about
8,000 feet above the sea ; to the west is a lower granitic range rising
* Becher, W. H., Mifi, and Mee. Mag,, 1892.
8KBTOH MAP 07
KINTA VALLEY
FEDERATED MALAY STATES
1006
SCALE OF MILES
ALLUVIAL TIN DEPOSITS OF THE MALAY PENINSULA.
27
some 3,000 feet, and separating the valley from the Strait of Malacca.
Between these ranges are lower mountains, and areas of limestone
surrounded and partly covered with great tracks of alluvium. Twenty
years ago the Kinta District was almost unknown, and Taiping and
Kuala Lumpur were the great tin centres, but now it is the most
important district on the peninsula. Among some of the more important
mining centres in the district are Kampar, Gopeng, Batu Gajab, Tronoh,
Cacha, Lalang, Papan, Lahat, Chongkat Pari, and Ipoh, the last being
the commercial centre of the district ; in fact, the alluvium over large
areas has been completely stripped from the bed-rock in search of tin,
and has been overturned in great piles, leaving the once fertile soil in
a condition of desolation."
*An ideal section of the main geological features of the Kinta valley
is given in Fig. 12. The valley is composed of a highly crystalline
limestone, usually white in colour, sometimes gray ; in fact, it may be
called marble. It is always highly inclined and often contorted, and in
some places is iuterbedded with shale. On the east side of the valley,
near its contact with the granite, it forms a remarkable series of lime-
Granite C^tUillin* Limvstone with Alluvial Granite
overourdcn
Fig. 12.— Ideal Section of the Kinta Valley.
stone cliffs, which rise in some cases as high as 2,000 ft. above the level
of the limestone in the valley. It is non-fossiliferous, and its geological
age is unknown. The mountains on both sides are composed of granite,
which is intrusive and has doubtless been the cause of the contortion
and metamorphism of the limestone, the latter appearing as though it
had been squeezed between the two intrusive masses. The granite is
gray in colour, and often porphyritic, with large, well-formed crystals
of orthoclase-feldspar, quartz, and biotite-mica. Tourmaline is very
common.
The whole valley and a large proportion of the mountain slopes are
covered with alluvium, which reaches a depth of 200 ft., as proved by
mine-workings, and may be deeper in the middle of the valley, where
there are very few workings ; the average depth is about 30 ft. This
* W. Rumbold, '• Trans. Amer. Inst. M. E.," July, 1903.
28 TIN DEPOSITS OF THE WORLD.
alluvium is composed of sand, pebble-beds and clay, and may rest either
on a bed-rock of limestone or of " kong."
The limestone, from its steep bedding-planes and contorted structure,
has been weathered to a very irregular surface, forming numerous
little pinnacles and depressions the latter often extending into cracks
of 10 to 20 ft. in depth, the whole forming an ideal series of natural
riffles.
*MoDE OF Occurrence of the Alluvial Tin in the Kinta
District. — In the larger valleys where the detritus from areas of
different rocks has been mixed, the tin-bearing alluvium is commonly
composed of a heterogeneous mass of white, grey, or red sandy or
gravelly clay, often of a mottled character, containing numerous small
quartz fragments about the size of a pea, together with pebbles and
boulders of granite, gneiss, schist, pegmatite, limestone, etc. The
alluvium in the hills, however, nearer its source, varies more in character,
distinctly reflecting in different places the nature of the different rocks
from which it has been derived. Frequently the alluvium is much stained
with iron, and often contains large quantities of vegetable remains and
partly lignitized wood.
The tin oxide occurs in the alluvium in a different way. Sometimes
it is scattered through it from top to bottom in comparatively uniform
quantities, sometimes it is in layers of rich ore separated by layers of
lean or barren ground, sometimes it is richest on the bed-rock, and at
other times higher up in the deposit. As a general rule, however, there
is a covering or " overburden," as it is called, of barren alluvium from
10 to 40 feet or more in thickness, and the tin ground is found beneath
this. The ordinary tin-bearing strata vary from 1 to 30 feet in thick-
ness, though sometimes they reach over 100 feet.
At the bottom of the alluvium is generally either granite or lime-
atone, though frequently where the tin oxide stops, barren alluvium or
rock decayed in situ separates it from the bed-rock, so that the solid
granite or limestone is not always seen. The limestone bed-rock is
often leached in undulating surfaces with alternating protrusions and
recessions, resulting in a series of natural riffles, behind which cassiterite
has concentrated. This occurrence is well seen along the waggon road
between Ipoh and Lahat, and is similar to the way gold has collected
behind limestone riffles near Columbia in California. Stanniferous
alluvium frequently occurs on ridges and hills as well as at lower levels
in the valleys and creek beds, sometimes suggesting that since the
formation of this alluvium there has been an elevation of the region
followed by subsequent erosion, with the result that the older stanni-
ferous alluvium occupies the higher places, while the younger alluvium,
derived probably in part from the older deposits, occupies lower levels,
in much the same way as the Tertiary gold placers of California often
occupy the higher spots, and the more recent placers are found in the
* W. R. Rumbold, " Trans. Amer. Inst. M. E.," 1906.
ALLUVIAL TIN DEPOSITS OP THE MALAY PENINSULA. 29
present stream beds. This may be true in some of the tin deposits,
but it is necessary to distinguish between such occurrences and the
cases where the tin deposits on the higher places are simply residual
deposits formed in situ by the superficial decay of tin-bearing rocks,
without removal of the tin from the region of its source.
Nature of the Tin Ore in the Kinta District. — The tin
occurs in the form of cassiterite or oxide of tin (SnOg) often well
crystallized in tetragonal prisms with fine termination, though the
fragments in the alluvium have been more or less rounded by attrition.
The ore varies in colour from black or brown to grey, greyish-green,
white, or transparent, but the commonest kind is of a dark brown colour
with a resinous lustre. Sometimes the ore is angular, and in compara-
tively large fragments; but this is rare, and the common alluvial tin
fragments range from the size of peas to that of sand grains or smaller ;
while efforts are being made to work tin ore that exists as a fine
powder in the mud banks that line certain parts of the west coast of
the peninsula.
The amount of metallic tin in the ore, as commercially mined, ranges
from 69 to 73 per cent., an average of about 70 per cent, being considered
very fair. The richness of the stanniferous alluvium varies much iu dif-
ferent places. The average value of the alluvium worked in the Kinta
District is probably about 1 per cent, of tin oxide, and the ground of this
grade pays well to work if favourably situated. If the alluvium contains
2 per cent, of tin oxide it is considered exceptionally good ground, and
with 3 or 4 per cent, it is considered remarkably rich. Sometimes
thin strata in the alluvium are very rich in tin oxide, containing from
40 to 60 per cent., but this is very rare.
Minerals Associated with the Tin Oxide in the Kinta District. —
With the tin oxide of the alluvium are associated much tourmaline,
hornblende, wolframite, and magnetite, while in smaller quantities are
found white mica, topaz, scheelite, sapphire, and it is said that in
parts of the peninsula small quantities of thorium and cerium minerals
have been found. Some beautiful transparent topaz crystals have
been found near Tapa, south of Cam par. Gold also has been found in
small quantities in the tin alluvium. Certain other minerals, such as iron
pyrite, chalcopyrite, bornite, and arsenical pyrites, which occur with
the tin in the rock, are rarely seen in the alluvium, as they have
decomposed, and mostly disappeared during the erosion of the rock,
though rusty masses of these sulphides, partly decomposed and asso-
ciated with quartz, often occur in alluvium which has not been
transported far from its source.
Occurrence of Cassiterite in the Hocks of the Kinta District, —
Though the tin mined on the peninsula comes practically all from the
alluvium, yet cassiterite also occurs in various places in situ in the
rocks of the region. It is most often found in granite, but also occurs
in the limestone and sandstone. It has been worked in a few localities.
30 TIN DEPOSITS OF THE WORLD.
but none of the efforts have as yet been more than partially success-
ful, and most of them have eventually failed, as the ore is in too
scattered a condition to pay to work. It seems not impossible, however,
that deposits may yet be found in the rock that can be profitably
worked.
Where the tin is seen in situ in the granite, it occurs in pockets,
small veins, or a combination of stringers intersecting each other in
various directions in the form of a network, while elsewhere the rock
is simply impregnated with particles and crystals of cassiterite over
certain areas. The tin is associated with quartz, tourmaline, fluorite,
and the other minerals already mentioned, especially iron pyrites and
arsenical pyrites, which often occur in very considerable quantities, and
smaller quantities of chalcopyrite. Cassiterite in the limestone is
probably rarer than in the granite, as Chongkat Pari was the only
case seen or heard of by the writer where it had been clearly proved
to exist in that rock. At that locality tin oxide occurs both in the
alluvium and in the limestone. In the limestone it occurs along a zone
of fracturing, sometimes as an impregnation in the rock, sometimes as
lenses or irregular pockets from 4 to 24 inches in width, and some-
times along the cracks in the rock, either longitudinally or transversely
with the zone of fracturing. It is associated with large quantities of
iron pyrites and arsenical pyrites, and smaller quantities of chalcopyrite
and bornite, and some rhodochrosite. At Bruseh, near Tapa, in Perak,
cassiterite has been found in thin seams and films along the lines of
bedding in a soft, fine-grained friable sandstone, which bears every
evidence of being a comparatively young rock, and it seems probable
that the cassiterire in it was derived from tin-bearing solutions from
the older rocks percolating along the bedding planes.
Origin of the Tin Deposits of the Kinta District. — The tin oxide
in the alluvium has clearly been derived by erosion from the cassiterite
in the rocks. As regards the cassiterite in the rocks, however, it may
be said that in the granite the occurrence of the cassiterite in veins,
stringers, network, etc., along lines of fracturing is strong evidence
of aqueous deposition of the ore ; while the occurrence as an impreg-
nation in the rock where no marked fissuring occurs may be due either
to concentration during a more or less molten condition of the rock, or
to aqueous concentration in a solidified rock. It seems probable that
the tin in the limestone was deposited from aqueous soluticm, in the
same way as at least part of the cassiterite in the granite.
Mr. J. B. Scrivenor, Geologist to the Federated Malay States, has
written the following account of the alluvial deposits at Taiping, in State
of Perak, and published in the " Perak Government Gazette," 1904: —
" The physical features of the neighbourhood of Taiping are well
marked ; and on account of their importance they call for a short
description here before dealing with the geological detail. The most
imposing of these features is the range of hills east of Taiping, trend-
ing at first north and south, and then turning slightly to the north-west.
It rises to three considerable peaks, Gunong Bubu, 5433'5feet (I quote
the names and elevations given on the 1901 Map of Perak, on the scale
ALLUVIAL TIN DEPOSITS OF THE MALAY PENINSULA, 31
of 4 inches to the mile) ; Wraj's Hill, 3,347 feet ; and Gunong Hijau,
4,751 feet 7 inches ; while at the northern limit of the range is a
smaller hill, Bukit Lara, 1,600 feet 7 inches. Between Wray's Hill
and Gunong Bubu is a pass leading to Padang Rengas, It will be
convenient to refer to this range throughout as the Taiping range. At
the foot of the Taiping range on the west are several smaller hills,
chief among which are Speedy's Hill, 964 feet, connected with the
Taiping range by a spur ; Scott's Hill, isolated, but sending out spurs
of its own ; and the hill on the southern end of which stands the
Catholic church. Another range, less imposing than that overlooking
Taiping, but, geologically, quite as interesting, lies eight miles as the
crow flies north-west of Taiping. This is the Semanggol range, cul-
minating in Gunong Semanggol, 1,279 feet 2 inches, and ending on the
north, at least as far as concerns us now, in three small isolated hills,
the most northerly being Bukit Merah. Between the Semanggol and
Taiping ranges are several small elevations. At Padang Rengas we
have an excellent example of a feature characteristic of the Peninsula,
the limestone hill Gunong Pondok, connected with the Taiping range
by a spur below the Waterloo Estate, but elsewhere rising sheer from
the flat floor of the Padang Regas Valley. For the rest, the area in
question, with the exception of that part in Selama, consists entirely
of a vast alluvial flat, from which has been extracted that wealth of
tin ore which has made the district of Larut justly famous.
" Nearly every writer who has dealt with the geology of the Malay
Peninsula has described the famous stanniferous alluvial beds at some
length. I do not think it is necessary to give a detailed account of the
mineralogical constitution, the order of deposition, and the thickness of
the various strata composing the mass of these presumably recent
deposits. I will merely dwell on certain points which I consider of
interest and importance, and some of which, as far as I am aware, have
not been touched upon by previous writers.
" The first of these points is the nature of the boulders and pebbles
in the tin-bearing karang, a matter of extreme importance, since thereby
it is possible to obtain valuable evidence of the source of the cassiterite.
In all the mines I have visited in the neiojhbourhood of Taiping small
heaps of pebbles were to be found washed from the karang in the
sluices, and almost invariably they proved of interest.
" Another point is the multiplication of the karang stratum. Evi-
dence of this was seen in two mines in Larut, one under Speedy's
Hill, where it was pointed out by Mr, Gumming that in working the
mine they had sunk through one bed of karang and found another bed
separated by alluvium consisting to some extent of light grey clay, and
which there was reason to suppose joined the higher bed some distance
off* ; the other, as shown to me by Mr. Gumming, in the Gugop dis-
trict, where at first a few feet near the surface were worked for tin
but later the mine was sunk to a deeper bed of karang, of great thick-
ness, and separated by strata and fine sand. Moreover, Mr. Gumming
informed me that in this mine one of the intervening beds, a thin layer
32 TIN DEPOSITS OF THE WORLD.
of coarse gravel, was found to contain tin in workable quantities ; so
that there are really three beds of karaug here.
" A very interesting mine, in connection with the question of the
derivation of the cassiterite, is now being worked by Messrs. Tate and
Gumming at Ayer Kuuing, close to the Small-pox Hospital. On the
west of the mine is the inconspicuous changkat on which the hospital
stands ; and a few furlongs to the east are the granite hills of the
Taiping range. Under the soil, in the western part of the mine, there are
15 feet of white overburden, which to the east give way to a more clayey
alluvium with numerous tree trunks. The white overburden consists
of loose kaolin, fragments of decomposed pegmatite, white and grey
quartz, and abundant pebbles of the shale and sandstone series bleached
to a light grey. There is a considerable quantity of tourmaline in
large crystals, which, together with associated quartz grains, probably
came from pegmatite veins ; and in places the alluvium is very mica-
ceous. It is remarkable that, in spite of the proximity of the granite
hills, the distance between the mine and the hills being much less than
between the hills and the Kota mines, where pebbles of granite occur ;
in spite of this, there was not a pebble of granite to be seen when I
visited the mine. Again, Mr. Gumming informed me that in working
the mine they find that the karang is shallow on the west, that is near
the changkat, while it gets deeper towards the hills. Now these facts
can only point to one conclusion, and that is that the white overburden
and the karang with the cassiterite have been derived from the small
changkat on which the hospital stands ; and further, judging from the
nature of the alluvium, it may be concluded that the changkat owes its
existence to a hardening of the shale and sandstone series, over and
above whatever may have been effected in this direction by the main
granite mass, consequent on the intrusion of a mass of pegmatite,
isolated on the surface, but certainly connected in depth with the other
igneous rocks of the Taiping range.
" Another point is the cementation of the alluvial karang by iron
oxides, which has taken place in varying degrees. In some cases the
karang is merely discoloured by limonite, and can hardly be said to
be cemented. At others, as for instance in Hong Hap's mine at Kota,
the karang, although cemented, is friable. Extreme cases were noticed
in two localities, one on the Jenah Valley, the other in the Relau
Valley, at Selama. In the Jenah Valley the karang was found in one
place to be so firmly cemented that it needed a smart blow of the
hammer to break it. At Selama, the base of a bed of karang, resting,
as far as could be learned from the available evidence, on decomposed
shale and sandstone, was also firmly cemented. The karang here,
which is exposed on a public dumping ground, is rich in tin oxide,
which can be seen projecting from the surfaces of the blocks of iron-
stone as rounded grains of cassiterite. This cementation may possibly
be due to the oxidisation of pyrites ; but a much more probable, and I
believe the correct, explanation is that it is owing to the oxidisation in
place of iron carbonate, which was deposited as chalybite from per-
colating water.
ALLUVIAL TIN DEPOSITS OF THE MALAY PENINSULA. 33
" My last point in connection with the alluvial deposits is the nature
of the kong, of which there are, in the Larut district, two distinct
kinds. The first is a mixture of kaolin and quartz in varying pro-
portions, according to the percentage of these minerals in the peg-
matite from which the kong was undoubtedly derived. This true
kaolin kong can be seen in two mines under the Sungei Ralau Tujoh.
The other kind of kong is found in the mines of the alluvial flat at
Kamunting and Kota, where it is found to consist of a dark grey, red,
light grey, or white clay, which may contain fragments of rock, as for
instance at the Chop Hiap Ju mine in Kamunting, where a borehole
revealed angular fragments of sandstone and fine conglomerate at about
12 feet from the surfp-ce of the kong, and at Kong Sing Lees mine at
Kota, where I was informed that the kong is in some places stony.
" In the existing literature mentioning the kong it is treated as if
it were of the same nature, and composed mostly or entirely of kaolin.
Thus Prof. H. Louis describes it as being generally an impure kaolin
formed by the decomposition of granite i?i situ,'^ M. De la Croixt
only speaks of the kougtay as a white plastic clay, which is very pure
kaolin. The Rev. J. E. Tennison Wood calls it kaolin, or partly
decomposed granite. | Mr, P. Doyle § speaks of it as a peculiar white
clayey substance which becomes friable on drying. M. Collet describes
the kontay as * kaolin (hydrated silicate of alumina),' as being nearly
always white or slightly tinted with blue, but sometimes dark red or
grey-blue when it rests on the schists ; and further, this author affirms
that such kontay is composed nearly entirely of kaolin.
" I selected two specimens of kong, one from one of the mines under
the Sungei Ralau Tujoh ; another of white kong from the Chop Hiap
Ju mine at Kamunting, a mine which is well out on the alluvial plain.
Microscopic examination of this material under a high power showed
that the former specimen consisted entirely of minute scales of kaolin,
with the characteristic irregular shape sometimes inclining to a hexagon,
the perfect cleavage parallel to the base, the index of refraction about
the same as balsam, and the weak double refraction ; while, on the
other hand, the Kamunting specimen consisted of a mass of quartz
granules, possibly some felspar, an occasional zircon, and a few grains
of brown tourmaline. There was nothing in the slide that could be
called kaolin.
" Thus, then, some of the kong at any rate contains little or no
kaolin, which will explain the failure of the manager of the Chop Hiap
Ju mine to use it successfully as china-clay. Of its real nature I do
not think there can be any doubt ; but to demonstrate this I must
* J. A. Phillips and H. Louis, " A Treatise on Ore Deposits." London. 1896,
p. B91.
t Op. cit.
t J. E. Tennison Wood, " Physical Geology of the Malay Peninsula "
*' Nature," Vol. XXXI., p. 152, 1884.
§ P. Doyle, " On Some Tin Deposits of the Malayan Peninsula," Guar Jour,
Geol, Soc, XXXV., 1879, p. 229,
34 TIN DEPOSITS OF THE WORLD.
anticipate somewhat and draw attention to the weathering of the shale
and sandstone series.
" I have already described how in the mine near the Smali-pox
Hospital the shale and sandstone is bleached to a light grey colour ; and
how under the hill on which stands the Catholic church the sandstone
is bleached completely. Further, in the railway cutting at Pandok
Tanjong the shalss are weathered to a pinkish, mottled, or white clay ;
and white clay derived from the same source, and similarly retaining
the bedded structure, can be seen in the small cuttings between Pandok
Tanjong and Kamunting. At Bukit Merah, too, the whole series is
lighter in colour than at Semanggol, owing to weathering. Weathering
in red-coloured rock is easily explained by the presence of oxides of
iron. But for perfect examples of this weathering it is necessary to
go outside the area under consideration and look at the sections of
similar shales between Bidor and Sungkai, where large masses in sitUy
retaining their bedded structure plainly, are bleached in some cases to
pure white, in others to pale purple, grey, or green. It is interesting
also to note that sedimentary rocks in Cornwall, not far removed from
these petrologically, have suffered an identical process of bleaching ;
and that so far no satisfactory explanation of it, so far as I am aware,
has been forthcoming.
" In view of the above facts, the simplest, and, as I believe, the
correct explanation of the koug at Kamunting is that it is the surface
of the shale and sandstone series, bleached either before or after the
deposition of the alluvium, and after the deposition of these beds, dis-
integrated by water percolating through the loose gravels above to
form plastic clay. It is possible that a portion of this kong immedi-
ately below the karang represents material that has been derived from
the shale and sandstone series at some place removed from its present
resting place ; but the angularity of the fragments of sandstone and
conglomerate shows that they at any rate, and the surrounding clay,
represent the series in situ.
" There is no evidence to show that the white kong, or the grey
or red, at Kamunting, has been derived from the granite range ; and,
on the other hand, there is plenty of evidence that the kaolin kong
under the Ralau Tujoh was formed in situ by the decomposition of
pegmatite. Therefore, with the possible exception mentioned above,
we may say that the kong of the Larut mining district represents
pegmatite and the shale and sandstone series decomposed in situ,'*'*
The Selaiigor Government Gazette of September 14, 1906, contains
a report by the Imperial Institute staff on a specimen of washed alluvial
tin ore from the land worked by the Sempam Tin Mining Company,
Pahang.
The ore consisted principally of a mixture of cassiterite, ilmenite
and monazite. The latter mineral was in the form of whitish opaque
grains unlike ordinary yellow monazite such as is found in Brazil and in
Carolina, United States of America. The washed ore as received was
found to contain tinstone equivalent to 50*86 per cent, of metallic tin,
ALLUVIAL TIN DEPOSITS OP THE MALAY PENINSULA. 35
and 1"51 per cent, of thoria. The following is the complete analysis
of the ore : —
Per cent.
Thoria ThO, 1-51
Stannic oxide SnO, 64*53
Titanic oxide TiO, 6*49
Zirconia ZrO, '48
Ferric oxide Fefi^ 3*09
Alumina AUO3 '24
Cerium oxide Cefi^ 3 '41
Lanthanum oxide LagOg ) . .00
Didymium oxide DigOg )
Manganese oxide MnO '36
Ferrous oxide FeO 2-36
Lime CaO '31
^, : : : : : :} ^-^^
Silica SiO, 2*44
Phosphoric anhydride PaOg 3*54
Loss of ignition - - - - - - - '81
Niobic oxide NbaOj,
Tantalic oxide TaJO^
96-81
Metallic tin 50-86
The monazite was separated from the other constituents, first by
magnetic means and finally by hand.
The " concentrate " thus obtained was analyzed with the following
results : —
Per cent.
Thorium oxide ThO, 8*38
Cerium oxide CCjOg - - . - - - - 25*46
Yttrium oxide Y.Og 2*80
Lanthanum oxide La^Og 1 qo.'to
Didymium oxide DigOg /
Ferric oxide Fe^Og - 2*78
Aluminum oxide AljOg '84
Calcium oxide CaO '61
Phosphoric anhydride P^Og 23-92
Silicia SiO, '92
Moisture H,0 -14
Loss of ignition 1*14
99-71
The results of the analysis of the separated monazite show it to be
rich in thoria, of which 8*38 per cent, was present,
c 2
36
TIN DEPOSITS OP THE WORLD.
The opacity of the grains of monazite is probably due to slight
decomposition, as is indicated by the presence of 1 per cent, of water
and by a deficiency of phosphoric acid, the amount of which is 24 per
cent, instead of 28 per ceiit. as would be expected in a monazite of this
class. A similar deficiency of phosphoric acid in relation to the rare
earths present was also noted in a previous specimen of heavy sand from
Tringganu which was sent to the Imperial Institute by the Government
geologist.
The proportions of the principal constituent minerals in the sample
are approximately as follows : —
Per cent.
Cassiterite --------65
Ilmenite (including rutile and magnetite) - - - 16
Monazite --------13
Columbite 3
Small quantities of other minerals were present but were not
estimated.
Conclusions and Recommendations,
? By magnetic concentration the constituent minerals of this tinstone
sand could be separated, and if this were done both the tinstone and the
monazite must be of commercial value. If, however, the ore were
smelted iu its present condition the monazite would be lost in the slag.
In view of the fact that the monazite is rich in thoria, its separation
from the sand on a commercial scale is worth consideration. Taking
the market price of tin at £180 per ton, the value of this ore as a source
of tin is about £80 per ton in its present condition. The concentrated
monazite would be worth, at the present rate, about £37 per ton.
* Chinese-owned Tin-Mines are much more numerous than may be
generally supposed, and may be enumerated as follows : —
In the Kinta Valley chiefly.
Mine. Owners. Coolies.
'Kampar - - - - Foo Choo Choon 1,200
Lahat - - - - ,, 1,000
S. Raia and Pulai - - „ 1,000
Chemoh - - - - „ 2,000
Chenai, T. Koyan - - ,, 500
Tronoh - - - - „ I^OOO
Papan - - . - „ 800
Salak - - - - „ 200
Tapah - . . - „ 200
Kumunting . - - „ 2,000
'Kota - - - - Ah Phin Bros.
1. <
Assamkumbang
\ Gopeng -
S. Siput -
I Kampar -
7,500
* C. DuucaD, Straits Echo, 19U5.
ALLDVIAL TIN DEPOSITS OF THE MALAX PENINSDLA.
37
Mine.
Owners.
Coolies.
Menglembu
- Cban Cboon Weng '
T. Rambutan -
" )>
3.
Cbenderiang
Papan
> 5,700
Tronob -
i»
Assamkumbang
" » >
' Cbenderiang
- Eu Tong Sen
4.
Tekka
T. Rambutan -
.3.000
, Kampar -
w >
5.
Temob -
- Cban Yek Tbeng
3,000
6.
Kamunting
- Ng Boo Bee
3,000
7.
Tambun -
- Leong Fee
1,000
8.
Kacha -
- Loke Mun Yeung
1,000
9.
Kacba -
- Cbang On Siew
1,000
10.
Kinta District -
- Li Tbung Sen
1,000
Cbinese miners employing less tban 1,000 men bave been left out
of tbe reckoning ; but it may be safely assumed tbat about 70,000
Cbinamen are earning tbeir living on small mines and by fossicking in
small parties in all parts of tbe States. Tbe ten Towkays above-
mentioned employ about 36,000 coolies, and it is no exaggeration to say
tbat tbe gross value of tbeir mines is represented by a sum exceeding
tbirty millions of dollars.
European
Mines.
Mine.
Owners. Coolies.
Gopeng -
New Gopeng -
Kinta Limited-
-
Limited Liability Co. 200
„ M 200
200
Red Hill
.
200
Pusing Lama - - - - „ „ 200
Papan (stopped work lately) - „ „ —
Tronob Mines (two-tbirds Cbinese) - - - - 1,000
Tbe following revision in tbe export duty on tin and tin ores
recently came into force in Selangor (November 1st), Perak and Negri
Sembilan (November 6tb), 1903 :—
Tin.
Per bhara.
Alluvial. — When tbe price of tin exceeds $31 per
pikulupto$32 $10.50
For every additional $1 per pikul in tbe price of
itin up to $38 25 cents.
For every additional $1 per pikul in tbe price of
tin thereafter ... ... ... ... ... 50 cents.
( 38 )
CHAPTER IV
THE ALLUVIAL TIN DEPOSITS OF BANCA, BILLITON
SIAK, SUMATEA, SIAM, BEITISH BURMA, AND
FRENCH INDO-CHINA.
•The most conspicuous tin-producing part of the Dutch possessions in
the Indian Archipelago is undoubtedly Banca, where tin was discovered
as far back as 1710; but since 1821, when the Dutch became fully-
possessed of this territory, Banca has been a very important factor in
the tin-mining industry of the world.
The tin deposits of Banca and Billiton, tjpical islands of the Indian
Archipelago, are mainly alluvial ; several unsuccessful attempts have
been made to work the lodes and stock works in these islands from
time to time.
In the island of Banca the geological conditions resemble those of
the Malay Peninsula. The bed-rock consists of granite masses flanked
by Silurian slates. Tin ore has been found occurring as impregnations
in the granite and also as yeins in the slate, but these deposits are
unimportant. The tin-wash consists mainly of fragments of granite,
"schorl," and sandstone. The bed-rock nearly always consists of
granite more or less decomposed. A section of an average stream-tin
deposit shows above the bed-rock three feet of tin-bearing gravel over-
laid by red sand, followed by red clay, then coarse sand with pockets of
clay, layers of fine sand with a little fine tin ore. The average over-
burden is from 25 to 35 feet ; shallow diggings are prospected by pits,
deeper ones by systematic boring. In 1903 and 1904 about 7,000 men
were employed in the mines of Banca, and produced an average of
nearly 72 per cent, of a ton per man. There is water for working in
the lower valley diggings but eight months each year, and for only
five months in the upper diggings.
The following account of the tin deposits of Banca is taken from a
book, " Banca and its Tin Steam Works," by P. Van Diest, translated
from the Dutch by C. Le Neve Foster, 1867 : —
" The stream tin occurs in valleys and on plains which are generally
alongside of the valleys, from where the tin is derived ; the true tin
ground, which consists of tin stone mixed chiefly with quartz gravel, is
found resting immediately upon the original bed of the valley. It is
* The Alluvial Tin Deposits of Siak Sumatra ; *' Trans. Am. Inst. Min. Eng.,'*
Vol. XX., 1892, pp. 50-84.
THE ALLUVIAL TIN DEPOSITS OF BANCA, BILLITON, SIAK, ETC. 39
rarely more than 3 feet, and usually 1 to 2 feet thick ; above the tin
ground there are various layers. First layer of coarse sand, then a bed
of clay, red, white, or black in colour. Above this a good deal of
coarse sand is met with, sometimes with much clay. Above the tin
ground there are usually beds of sand, upon which follow beds of clay,
the fine light particles of which were held longer in suspension than
the sand. Between them there is sometimes a thin bed of sand
containing a little tin. The total thickness of the over-lying bed is
seldom more than 33 feet, and usually from 16 to 33 feet ; above these
beds there is a layer of soil in which the river or brook takes a shallow
serpentine course. The tin -bearing valleys are usually broad and
marshy, especially in the granite country.
*' The bed of the river is, as a rule, immediately above that of the
original valley ; the deposits on the plains consist merely of a single
bed, the whole of which is tin-bearing. Sometimes, however, a true tin
ground is found covered by a layer of soil, and occasionally also by a
thin bed of clay. These deposits, which are not in the valleys, are
called Kool it-grounds in Banca."
Whenever it is proposed to begin a stream work, a dam is made
at a certain distance up the valley. A reservoir is thus made, and leats
coming from it are dug on both sides of the valley.
A large portion of the lower part of the valley is then laid dry by
another leat or drain, which is usually dug near the bottom of the
valley. This drain runs some distance below the first pit or kollong.
The other leat should be placed as high as possible, and serves to bring
water to wash away the overburden and drive the water-wheels to
pump the kollongs dry. This leat is called the " bandar " ; as soon as
these arrangements are completed the working of the first kollong is
begun.
The work is nearly always carried up the valley. The kollongs are
usually oblong, and so long that it takes years to dig them out and
obtain the tin. A workman can remove on an average of nine hours'
work per day 350 to 530 cubic feet of ground to a depth of 3 feet
3 inches. When the upper part of the overburden has been removed,
moveable launders are arranged with streams of water running through
them ; a number of workmen then shovel the gravels into these
launders ; for this purpose they use shallow baskets with long handles ;
the baskets are filled and placed within reach by workmen who are on
a lower level, and who loosen the ground with crowbars and " patjols."
On an average two men, one filling baskets and the other emptying
them only, can remove a piece of ground 6 feet 7 inches square to a
depth of 6 feet 6 inches, or about 282 cubic feet.
The beds which lie below the level of the stuff removed in this manner
cannot be got away by means of water, but have to be carried up.
The tin ground itself is carried to a separate place where water for
washing it can be conveniently brought ; looking from the side of the
kollong these carriers seem to form an endless chain.
Nothing but chain pumps to overshot water-wheels are used
in Banca. They are arranged in a very practical manner, and
40
TIN DEPOSITS OF THE WORLD.
their construction agrees perfectly with what theory shows to be
correct.
On an average 141 cubic feet of water can be raised 16 feet by a
pump which requires 106 cubic feet of water to work it. Four
hundred and seventy-seven cubic feet are pumped up in a minute out of
a kollong 14 feet 9 inches deep by three water-wheels.
Underneath the tin ground rock in places is met with. It is much
decomposed, and called by the Chinese " kong," i.e., empty.
The kong consists entirely of decomposed granite. The felspar of
the granite is usually entirely decomposed wiih kaolin ; the mica is
generally entirely weathered away. The tin gravels are sluiced by a
powerful stream of water, in which the stuff is stirred about in small
quantities, the tin settling down and cleaned by drawing it up against
the stream by means of the patjol ; experienced workmen do this very
nicely and smoothly.
In the province of Soengei-Liat, the ordinary mines remove 10,600
to 14,000 cubic feet a year for each person employed.
- A
Fig. 13.— section Alluvial Ore deposit, Banca.
A. Decomposed rock in situ.
H. Tin ground (tin stone with pebbles of vein stone).
C. Bed of coarse sand. Sometimes mixed with clay.
D. Running sand and beds of sand mixed with clay in varying proportions.
E. Beds of clay sometimes mixed with sand and soil.
F. Surface sub-soil.
Geology of the Doeren District. — At the two hills, Lampor
and Sambong Giri, the beds of slates are hardened and very much bent
and contorted, causing an apparent multiplication of alternate blue and
white layers ; near the granite we find a porcelain jasper, lydian stone,
and a hard slate.
To the north of the mining district of Doeren a mica schist occurs ;
the slate here contains a great deal of oxide of iron, which occasionally
appears as a bed of iron ore. In the province of Blinjoe especially.
THE ALLUVIAL TIN DEPOSITS OF BANCA, BILLITON, SIAK, ETC 41
these ferruginous slates occupy a considerable extent of country along
the borders of the granite.
Near Brang, in the province of Muntok, white tin stone is found to
occur in veins of quartz and also in separate veins ; in this province the
bed of ferruginous slate is very limited. The granite has broken
thiough sandstone, which has suffered considerable alteration.
Granite rocks of Banca : — The granite at Cape Poence is less
coarsely grained than that of Obi Lui. The mica is more prominent
and brown in colour ; the felspar a brilliant white, sometimes a dull
green, with small veins of quartz and tourmaline.
At Cape Raja little veins are met with consisting of a soft silicate
of alumina mixed with quartz. Veins of a fine-grained granite and
sometimes found in ordinary granite, a little copper pyrites with a
coating of carbonate of copper, were ol)served in some of the joints ;
between Cape Lajang and Cape Raja is the Bay of Soengei Liat, in
which the Liat River discharges into the sea.
Near Sambong Giri in breaking a piece of sandstone I saw unmis-
takable crystals of tin in the joints ; this was the first time tin had been
found in lodes. In a trench cut at Sambong Giri, a lode was discovered
dipping at an angle of 70 degrees, much the same as the beds of quartz,
etc. ; five feet below the surface the lode opened out, but not for any
great length ; rich tin stones a foot thick were obtained from it. The
sandstone beds near this deposit of tin are contorted.
From all the investigations made, the following inferences may be
drawn with safety : —
(1.) In Northern Banca tin occurs in the granite in various ways,
and over a large extent of country.
(2.) The rocks which surround the granite are impregnated with ore
and other minerals occurring in the granite for some distance, usually
not more than about one mile and a quarter.
(3.) The materials are chiefly deposits in little veins or bunches in
the direction of the planes of bedding or in the joints,
(4.) It is chiefly sandstone which takes up these minerals where the
rock appears to be most metamorphosed. If, on the one hand, the
peculiar occurrence of tin in the rock enables us to explain the great
extent and uniform thickness of the stream tin deposit, on the other
hand it enables us to surmise that no regular workable tin lodes occur
in Banca.
The first thing in searching for stream tin in Banca is to trace the
boundaries of the granite. Then carefully examine the rocks which
occur round the granite in order to be satisfied that the valleys to be
operated on are most richly filled with stream tin.
Concerning the origin of the tin deposits found in the Island of
Banca^ M. De Groot, chief of the Mining Department of the Dutch
East Indies, in a letter to Sir R. J. Murchison, as far back as 1863,
writes as follows : — "Twelve years ago, when I first arrived in Java,
it was generally considered that the stream tin found in the Island of
Banca was not derived from veins in the granite of the island, but from
mountains on the continent of Asia, whence it had been washed down
42 TIN DEPOSITS OF THE WORLD.
to the bottom of the sea, and that the sea-bottom had been subsequently
upheaved so as to form the island of Banca. This supposition appeared
to me erroneous, and I therefore endeavoured to collect facts bearing
upon the question. In 1860 I inspected all the stream works in the
island, and found in the district of Pancal-pinang three parallel veins
running nearly east and west, one of them containing tin ore in jjrains
like those in the stream works. In 1862 I surveyed the Jeboes district
and found grains of tin ore disseminated in granite. I also found that
in every river that was streamed for tin the largest grains were found
nearest the hills, and that further away towards the sea they gradually
became smaller. Now, as the rivers of Banca run from the interior in
all directions towards the sea, these facts proved that the stream tin is
the detritus of the rocks and veins containing tin-ore occurring on the
island."
With regard to the conditions of labour in the tin islands, it is
officially pointed out that there are in Banca many thousands of miners,
consisting mostly of the lowest and most disorderly classes of Chinese,
and that nevertheless order is satisfactorily maintained in the island,
which occupies an area of 200 square geographical miles, by a scattered
police force of 244 Malays. Some ten years ago there was a sort of a
mutiny, but it was quickly suppressed. It is a fact, however, that
within the past few years there has been a falling-ofF in the number of
Chinese coolies imported into Banca. In 1890 the number of coolies
employed was about 6,500, but in that year the regulations affecting tin
mining were modernised, with the result that gradually the number
doubled, until in 1899 it reached 12,107. In the past two years, how-
ever, the arrivals have fallen to about 900 a year, and it is probable
that this is due to the competition for Chinese labour in other parts, not
especially South Africa, but rather in the tin mines of the Straits
Settlements. It has now been decided to render the conditions of the
Chinese labourers in Banca more easy by raising the amount paid by the
Government for the tin delivered from the mines by 25 per cent., though
as apparently this increase is to be paid to the Chinese labour con-
tractors, each of whom supplies and controls a number of miners, it is
doubtful if the actual labourers will obtain any considerable part of it.
Billiton. — In Billiton, also under the 'Dutch Government, the
geologic conditions resemble those in Banca. There are granite masses
surrounded by quartzites, schists, and slates of Silurian age. Some tin
is obtained from ledges that occur both in the granite and in the
quartzite, but the greater part of the tin comes from alluvial deposits.
In 1903-4 about 8,000 men were employed here, the output averaging
per man a little under seven-tenths of a ton of tin. The prospecting is
done very systematically, and is in charge of a corps of European
engineers, who test the fields in advance of the mining operations by
boring first at intervals of, say, 100 yards, and supplementary holes are
made from 20 to 25 yards apart to ascertain the course, average thick-
ness and character of the pay gravel. The contents of each hole is
carefully washed and the tin ore weighed, and from these results calcula-
tions as to the probable yield of the ground are made. No lode
THE ALLUVIAL TIN DEPOSITS OF BANCA, BILLITON, SIAK, ETC. 43
mining of importance has been undertaken. As far as the author
is aware, there is no British Company operating in either Banca or
Billiton, and the mining there can be regarded as practically a Dutch
monopoly,
* In the small island of Singkep, close to Billiton, stanniferous
alluvial deposits occur in some of the valleys, notably in those of Daba
and Jankang ; these are worked by a Dutch company, the Sinkep
Tinmaatschapij, who employ about 450 miners.
(1) The tin deposits of Siak in Sumatra were leased + to a Dutch
syndicate "for the extraction of tin and other minerals which appear in
that part of the dominions." All the inhabitants working the tin-
deposits in this region are obliged to pay a tax to the Sultan on the tin
produced.
Sumatra is divided longitudinally by volcanic ranges into the east
aod west coast country. The west coast is a narrow strip of land
20 to 30 miles wide, underlaid, according to Dutch geologists, with
granite ; in places it is covered with alluvium and coral formation,
sandstones, slates and volcanic rocks. East Sumatra is a generally low
and slightly undulating country with superabundant rainfall, and little
is known of its geology in consequence.
The tin-fields of Sumatra are approached by steamers of 12 feet
draught, running from Singapore across the Straits of Malacca to
Brewer Straits, up the Siak river to Benkalis, then south to Siak and
east to Packanbarve. The distance up the river to Packanbarve is,
according to the captain of one of the steamers, 120 miles. Beyond
Packanbarve the Siak river becomes very sinuous and shallow, necessi-
tating the use of hloncong^ or partially covered canoes of a similar type
to that used on some streams of South America. These canoes are
propelled by poling or rowing as the case may require.
The cost of transportation — part by steamboat, part by canoe,
entailing the breaking of bulk, the use of store-houses, &c. — is naturally
a heavy charge against any enterprise commenced in this district, owing
to the risk of floods, drift timbers and other incidental dangers. Thus
it happens that any enterprise undertaken near the interior of Sumatra
is for the present confronted with rather formidable obstacles and
disadvantages, involving he"avy initial costs which can be offset only by
extraordinary richness of the natural resources to be developed. The
present centre of operation in the eastern tin-fields is Kotta Rannah,
lying about 300 feet above the sea, and connected by a track not more
than 15 miles long with the Siak river station Getti. Over this track
all freight is carried on the backs of the native Malays. The track is
bad and presents many difficulties. As compared with Banca, Billiton,
and other tin-producing competitors, Kotta Rannah, owing to the transfer
difficulties referred to, cannot compete favourably at present. The
underlying portion of this part of the country, so far as can be judged
* Phillips and Louis, " A Treatise on Ore Deposits."
t Tbe Alluvial Tin Deposits; Siak, Sumatra. " Trans. Am. Inst. Eng.," Vol. XX.,
1892, p. 50-84.
44 TIN DEPOSITS OF THE WORLD.
from the colour and nature of the soil on the paths, is sandstone. At
and east of Getti an indurated calcareous clay, full of cypridenas and
other small shells, forms the shores of the Tapong Kiri. The clay-
matrix surrounds rounded quartz granules, from the size of a pin's head
to that of a pea, and more angular and partly kaolinised pieces of
felspar. Throughout the mass occur carbonised vegetable remains and
some shells. Inland, up and down the Siak river and west of the town
of Siak, the soil is very clayey, so much so, in fact, that tobacco-growing
has been abandoned on account of it.
A comparison of the foregoing account of Sumatra with what is
known of adjacent countries shows that similar geological conditions
have prevailed in the Malay Peninsula, Karimon Islands, Western
Borneo, Sinkep, Banca, and Billiton, and as the search is extended, this
belt of a geological unity will unquestionably be widened. Quartzites,
quartz conglomerates, quartz, schists, hornblende schist, siliceous sand-
stones, clay-slates, with granite and local basalts, form the prevailing
rock formations.
The Kotta Raonah-Rambai stream-system and banks for alluvial tin
possess a universally shallow and similar alluvial covering.
The covering over the angular quartz gravel averages 3J to 4 feet,
and consists of about 6 inches of humus and o to 4 feet of yellow sandy
clay. The underlying angular quartz gravel is itself divided into two
separate layers. The upper 8 to 10 inches consists of angular frag-
ments of white quartz of 3 inches maximum and 1 to 1 J inch average
diameter, largely intermixed with carbonised wood. It carries very
small amounts of fine cassiterite, and considerable magnetic and red
oxide iron-sand. In the lower layer, which is separated from the upper
by a thin, often only slightly-marked seam of grey clay, from 1 to 2
inches in thickness, the nature of the quartz gravel is the same as above ;
but carbonised wood is absent, the amount of iron-sand is smaller, that
of cassiterite is larger. This layer is locally known as the pay seam.
Small crystals or crystallme fragments of spinel and ruby, but no
tourmaline, garnet, topaz, or mica were noticed. Both the tin-ore and
the quartz show little average wear of corners and edges, indicating
that they have been transported a short distance only.
Underlying the quartz gravel is a tough grey or greenish grey clay
of varying thickness, which gradually passes into decomposed rock in
places from 3 to 4 feet thick. Below this lies the true bed-rock, an
impure sandstone of the nature already described.
The tough grey clay underlying the quartz-gravel is the bed-rock
for working purposes.
As is usual in creek-beds and their adjacent banks, unevenness in
the bed or pot-holes occurs, in which there is generally an extra accu-
mulation of tin-ore. In figuring the thickness of the gravel and its
corresponding richness they must be considered. By a simple compu-
tation (the tons of quartz-gravel worked from a given area being known)
one can arrive at the conclusion that the average thickness of the pay-
quartz gravel, including the pot-holes, is about 6J inches, or 0*54 feet,
in the Batang creek, with an average overburden of 4*93 feet.
THE ALLUVIAL TIN DEPOSITS OF BANCA, BILLITON, SIAK, ETC. 45
This creek was selected to begin operations on as offering the best
inducements. The pay -gravel yielded '* black-tin " (averaging 70 to 72
per cent, in ** white " or metallic tin) at the rate of 2yV pounds per ton
of 2,240 lbs., or 0*12 per cent. Calculated on the total amount of
ground excavated, including the stripping, this would be 0'476 pounds
black, or 0*348 pounds white tin per cubic metre excavated. In Banca
the same amount of excavation (according to Von Diest) yields 2^ to
3 J kg. black, or 1 J to 2-03 kg. (2-95 to 4*46 lbs.) white tin.
The relative proportion of pay-gravel to entire stratum reserved is
at Banca 3 to 33 feet ; at Kotta Rannah 0*54 feet to 5*47 feet, or practi-
cally the same. The advantage of a lighter covering in the latter place
is neutralised by a reduction of yield in about the same proportion.
The economical limit of mining is naturally different in the two places,
depending largely on surrounding conditions, mechanical facilities, and
the cost and efficiency of labour.
From geological indications it is apparent that the Kotta Rannah-
Rambai alluvial tin -field is of comparatively recent origin, being derived
from the broken-down outcrops of stanniferous quartz-veins which occur
in the underlying and adjacent impure sandstone, in a probably north-
west and south-east direction. They are likely to extend at intervals
into adjoining districts Unquestionably there are other and similar
belts in Siak. Tin-ore has been found in the streams of the north-west
part of the concession and beyond, near to Rokhan river, but little is as
yet known as to the extent and value of the lodes. A systematic
tracing of the belt may lead to the discovery of richer fields in Siak
than the one described.
The hours of work in Siak are from 7 to 11 a.m. and from 1 to
5 p.m. Coolies in Siak are paid once a month, nominally $2.50, but
$1.50 is kept back on account of the advance made on enrolment,
leaving the coolie $1 in cash per month during his year of employment.
In addition to the Chinese miners, small numbers of the Javanese coolies
are employed in Siak for making roads and grubbing out the roots of
trees, and the native Malays find work in clearing the jungle and forest
and carrying supplies over rough roads, etc., etc.
The Banca miners of alluvial tin distinguish two classes of work :
the mountain stream work, called kulit, and the working of valley places
and flat, called kollong. In Siak, Sumatra kulit-work only exists.
This work is performed, after the necessary preliminary cleaning and
grubbing, by Chinese coolies, and consists in first diverting the stream,
and then making, stream upwards, a series of rectangular excavations
(kulit).
Tin Deposits of Siam.
Tin is the only metal the working of which is of any importance in
Siam. Tin is found in small quantities in the valley of the Nam Sak
river and in various places in Northern Siam, but all the deposits of im-
portance are derived from, and lie adjacent to, the great line of granitic
upheaval which forms the boundary range between Central Siam and
Tenasserim, is the backbone of the Malay Peninsula, and may be traced
46 TIN DEPOSITS OP THE WORLD.
down to the Dutch islands of Billitou, Banca and Sinkep. This great
line of granite is the source of practically all the vast alluvial deposits
of tin which are found in Siam and the British and Dutch East-Indian
possessions. The Siamese territory is probably as well off in this
respect as either the British or Dutch, and the deposits are very widely
distributed. Of the Siamese possessions in the Malay Peninsula, tin is
at the present time being worked in the following provinces : —
East Coast. West Coast.
Ratburi. Kra.
Bangtaphan. Renong.
Langs uan. Takuapar.
Chaiya. Pang a.
Bandon. Takuatung.
Lakon. Puket.
Jalar. Trang.
Ranjeh. Stul.
Rahman. Perlie.
Kelantan. Kedah.
Tringganu.
In some of the provinces the works are very small and unimportant ;
but the total annual production is little short of 5,000 long tons,
of a value of about £950,000, taking the price of tin at £190 per
long ton.
Generally speaking, all the mining is in the hands of Chinese, the
labour is Chinese, and the smelting is done locally by Chinese methods.
The only exceptions to these generalisations are that one British and
one Dutch company are working in Kedah, an American company is
making a small commencement in Bangtaphan, and a British smelting
company is establishing an ore-buying agency in Puket. The number
of Siamese and Malays engaged in tin-mining is very small.
There is an enormous field for the expansion of the tin-mining
industry in the Siamese possessions in the Malay Peninsula ; and con-
siderable activity in prospecting on the part of European capitalists
has lately been shown.
At present, Puket Island (on the West Coast) is the most important
tin-mining centre in all the Siamese States ; but Kedah, Takuapar,
and Renong (also on the West Coast) have a considerable mining
industry. On the East Coast, Lakon Sri, Tammarat, and Jalar (Port
Patani) are the chief centres. The most promising districts for future
developments are in Kedah, Rahman, Jalar, Takuatung, and Renong.
Tin Deposits of British Burma.
* Mr. T. W. Hughes-Hughes, of the Geological Survey of India,
writing on " Tin Mining in Mergui district at Kahan," states there is
* "Geological Survey of India," Vol. XXII., Part 3, 1889.
THE ALLUVIAL TIN DEPOSITS OF BANCA, BILLITON, SIAK, ETC. 47
no vein-bearing ore, but a bed of felspar of from 4 to 6 feet in thickness,
scattered through which were specks of black lin in very irregular and
meagre amount.
At Tharupin, 32 miles from Mergui, and situated, like Kahan, on the
right bank of the great Tenasserim, there is a fair chance of meeting
stanniferous deposits.
Near BCkpjin there are some stream works, and tin ore exists here
in sufficient quantities to pay for extraction. The ore bed in the cut-
tings varied between 5 and 6 feet in thickness, and was overlaid by
about 10 feet of top soil. The mines about here are all owned by
Chinese and Siamese. At TCnbyan tin lode stone was formerly worked.
At Thabawleik a cutting gave the following measurements : — Top
soil 6 to 10 feet, then a strong pebble and boulder bed of slate and
sedimentary rocks with highly charged stanniferous clay 8 feet below.
Quartz fragments are rarer in the pebble bed here than at Taiping,
Renong, and BOkpyin.
The mining operations are carried on in the ordinary way. About
200 Chinese and Siamese are employed in the Baichuni mines. Here
the ore bed is 6 to 8 feet thick, and fairly rich ; the whole district is
capable of extensive development.
Karathuri : The ore beds here vary from 8 to 12 feet in thickness of
good paying character, and water is fairly abundant.
Coolies are paid 42 dols. per year for 360 working days, food free.
At Chaungtanaung the stanniferous stratum is only 3 feet in thickness,,
and poor quality.
At Yamon the ore bed is 2 to 3 feet ; not much mining being carried
on in these districts.
At Maliwan the ore is said to yield better than at Ren6ng. An
English company attempted some lode mining here in 1873, but the
venture proved a complete failure.
Dr. Oldham says in 1855, "The principal source of the ore is the
extensive deposits of stream tin."
Mr. Mark Frayar, in 1871, was struck with the wonderful extent of
the distribution of stanniferous detritus.
The progress of mining in the Mergui district has in the past
not answered the expectations of the Government, and Mr. Hughes
advises liberal conditions of acquiring concessions, and assistance for
prospecting and placing of ore.
Tin deposits occur on the watershed of the Khamaungthwe River,
a northern tributary of the Great Tenasserim River, east of Tavoy.
The following account is taken from the reports of Messrs. GilfiUan
and Cox on this district : —
Location and Area, — The Southern portion of the j)roperty is
situated about 30 miles inland from Tavoy, an important town located
on the estuary of the river of the same name.
It embraces an area of about 350 square miles, being the watershed
of the Kamongthway River and its numerous tributaries, and extends
north at Myitta some 35 miles, where the two high ranges forming
its Eastern and Western boundaries converge on the borders of Siam.
48 TIN DEPOSITS OF THE WORLD.
The Kamongthway unites with the River Beau at Mjitta to form
the fine waterway of the Great Tenasserim River, which, flowing East
and then South, bending North again, flows into the sea near Mergui.
Physical Features, — Some of the higher peaks of the boundary
range are over 4,000 feet high, but the general average is les4 ; the
foot-hills and higher spurs are about 3,000 feet, while the elevation of
the valley is about 2,500 feet.
The Great Tenasserim River below Myitta is 500 feet wide, but if
is not navigable except by small boats during the driest months, on
account of its rapids.
The Kamongthway above Myitta widens out in places to over 300
feet, has frequent shallows and gravel beaches ; but even during the
driest part of the year it is several feet deep, with fine pools 8 to 14
feet deep.
Some of the tributaries are fairly large streams, with well-defined
banks ; but their tributaries again are in many cases mere streamlets,
becoming dry, or a series of pools, during the driest months (March and
April).
The valleys of these streamlets, when ascended towards their source
in the foothills or intervening ridges, gradually become narrow and
more gorge-like, so the readily available area for alluvial mining becomes
diminished. There are some fine flats adjacent to the main streams.
During the rainy season (June to November) some 200 inches of
rain falls ; then the whole of the river system is flooded, and the lower
Ijiug grounds inundated. With the cessation of the rainfall this water
gradually drains off, the streams rapidly diminish in volume, and the
smaller ones become dry.
The general water level thus descends from its maximum height
attained about October-November, to its minimum about the end of
April.
Sluicing operations can consequently be carried on most readily at
the sources of the streams, and on the higher gravels, during the rainy
season.
Shaft-sinking and the removal of the stream and lower gravels,
without dredgers or mechanical appliances, can be carried on most con-
veniently after the termination of the rains, the hydraulic mining opera-
tions gradually being advanced towards the main stream as the water
drains away.
The gravel beaches of the main stream could be sluiced during the
driest month.
Geology. — There are few rock exposures even in the bed of the
streams, so geological examination is difficult, and sufficient data have
not yet been obtained to complete a map or form definite conclusions.
The Western boundary ridge consists of granite, which also outcrops in
various parts of the concession. Where the telegraph line crosses
the Western boundary the granite is overlaid by a series of highly
inclined stratified rocks, while eastwards, about four miles north of
Myitta, a newer and less inclined series of fissile slates has been noted.
Timber — The whole of the area is densely jungled with bamboo
THE ALLUVIAL TIN DEPOSITS OF BANCA, BILLITON, SIAK, ETC. 49
and other tropical plants. Some fine timber, suitable for all miniDg
purposes, grows in many parts, and can be cut on payment of a small
fee for the more valuable kinds.
The Golden Stream District,
The Golden Stream, or Schwey Chaung proper, is a small tributary
on the North bank of the Hindu Chaung proper, a stream which at the
time of our visit was not of great importance, but which flows east-
ward, joining the Khamaongthway approximately one mile above the
Myitta township.
The whole of the country in this neighbourhood is relatively flat,
but small ridges occur dividing the different streams.
The Hindu Chaung itself, when we were on the ground, consisted
of a series of water-holes with small streams connecting them, and the
tributary streams are so flat that they were hardly flowing at all.
During the rains, however, there can be no doubt that all these streams
are of much greater importance, and a large volume of water flows
through the valleys.
The whole of this area is covered with soil, below which there are
deposits of a tough plastic clay of varying thickness, and underlying
this there is a gravel wash in the valleys which generally crops at or
below the level of the streams, so that it is only where the streams have
cut banks that the gravel can be tested without sinking ; but wherever
these gravel exposures can be got at, tin stone in greater or less quantity
can be obtained by panning, and, in many cases, gold can also be seen in
the dishes after panning off.
It is, of course, impossible where the gravel can only be got at in
such a way to form quantitative estimates of its metallic contents which
could be absolutely depended upon, and all we can say is that we
washed samples from a number of places, some of them miles apart,
which showed prospects quite good enough for sluicing or dredging.
At the Golden Stream itself some clearing has been done, and a few
shafts sunk through the clay until the gravel has been reached, and
while we were on the ground we had some stripping done, and the first
bed of the gravel sunk through so as to form some idea of its value.
At the particular spot where our tests were made there was an
overburden of about eight feet of soil and clay, below which about three
feet of coarse gravel carrying tin and gold occurs.
Below this, again, there is a finer water-worn wash in which the
yield is much less than in the three-feet bed, but with the appliances
available we were unable to get through this on account of the water,
and consequently were unable to prove whether or no other coarse gravel
deposits underlie this first one, or to determine whether and where any
gutter exists.
In dredging, this finer gravel would be treated with that overlying it,
and dredging would be the most convenient method of dealing with the
deposits in this district, as there is no fall for sluicing. Panning results
of the soil and clay overlying the gravel showed very small quantities
50
TIN DEPOSITS OF THE WORLD
of tin and gold, but the material would be extremely difiScult to handle
mechanically either by dredge or sluice, and we think there is no doubt
it would have to be removed either by hand or mechanical excavators
before dredges were set to work.
As regards the value of gravel, we washed a section 4' by 4' by 3'
RANGOO
<
. \C6)|rCESSlON
TAVOY\ /1p
CO
BANCKO
Locality
Plan.
PIG. 14.— Plan showing Tin Deposits of British Burma.
deep, which yielded 5*84 lbs. of concentrates = 3*28 lbs. per cubic yard,
and this sample when assayed yielded : —
Gold. ... 11 ozs. 7 dwts. 1 gr. per ton.
Silver . . . 1 „ 6 „ 22 „
Tin (metallic) 55 per cent.
THE ALLUVIAL TIN DEPOSITS OP BANCA, BILLITON, SIAK, ETC. 51
♦
In the Hindu Chaung stream itself, wherever gravel is exposed, tin
is found in the wash, but with much less gold than in the Golden
Stream. We had samples panned from several places, and made one
test of seven dishes which appeared about an average of what could be
seen. These seven dishes = If cwts., yielded 4 ozs. of concentrates of
4*2 lbs. per cubic yard, assaying : —
Gold . .
. . 18 dwts. 16grs. per ton,
Silver . .
. . 14 „ 5 „ „
Tin . .
. . 67 per cent..
or reduced as before to the 70 per cent, tin basis, 4*02 lbs. of concen-
trates containing 70 per cent, tin and 19 dwts. 11 grs. gold per ton.
The value of these concentrates is £79 Is, Id, per ton = 2«. \0d, per yard
of gravel.
Labour, — During the first month the local inhabitants (Karens) were
employed, and some of them worked remarkably well for 18 rupees per
month, but in January most of them left, being unused to continuous work,
and being desirous of attending to the cultivation of their plots of new
ground. A few of them have continued to accompany me when pro-
specting, and are excellent men for that class of work or jungle clearing,
but they decline to do shaft- sinking or earth-removal work. Some
coastal Burmese were engaged, but as they could not get the food supply
that they were used to, they left. Generally speaking, although some
local labour may occasionally be obtained, still it cannot be relied on for
continuous mining work. Two gangs of Indian coolies, Pathans and
Keringues, were engaged, without adequate selection, by a labour
agent in Rangoon, the rate of wages being 25 rupees per month for the
former, and 20 for the latter. Some of these men worked M'ell when
under European supervision, doing as much work as many white miners
would do under more favourable circumstances.
Climate. — The climate is tropical ; the months of December and
January were not unpleasant, and the nights were cold, with a dense
fog. In February and March the weather was warmer and more trying,
and before the break of the monsoon was specially so. In May the heavy
rainfall commenced, which will last till November.
At Henzai Batin N. of Tavoy, a promising alluvial deposit containing
crystals of cassiterite has recently been located by Mr. G. D. Ricketts.
* The Khow Maung District, — The property is located in Lower
Burma, situated near the Maliwun River, which, being navigable, offers
easy access to the sea at Victoria Point, a distance of about twenty
miles.
Mr. A. D. Snow writes as follows : — " I have found what appears
to be one of the most extraordinary combinations of lode and alluvial
tin that have been discovered in any part of the tin-producing East
Indies. Not only have we the most important factor for successful tin
mining — a big tin lode and rich alluvial deposit — but we have also
natural facilities, such as water power, timber, and a good climate to
* " Mining Journal," Oct. 13th, 1906.
D 2
.62 TIN DEPOSITS OP THE WORLD.
f
assure cheap production. Tin has been known to exist in the Maliwun
dislirict for many years.
"The area of the Khow Maung tin-bearing zone is so extensive
that one hardly knows where to begin, and it is not likely that even the
most practised and industrious prospector could at once strike the richest
part of the tin ore on the Khow Maung Hills. In my first adit at
Centre Hill, where I cut the formation at right angles over a distance
of 268 ft., I found the surface tin quartz strata to continue downward,
and to carry in value about the same per cent, of tin as the same strata
contained on the surface. Although I could not find in the length of
this adit values high enough to justify a favourable report, I have made
this valuable discovery — that every one of the quartz strata that showed
on the surface has been cut underground by our adit, and is still con-
tinuing downward ; thus we have a fair right to suppose that all the
tin -bearing rock of the Khow Maung zone will be found to be as rich
under as on the surface."
* Stanniferous Deposits in French Indo-China.
These remarkable deposits occur in the valley of the Nam-Patain, a
small stream which runs into the Hinbun, itself a tributary of the
Mekong. This valley lies in what the author terms the Middle French
Laos, the country which extends along the left bank of the great river
just named, between Annam and Siam, and north-east of Cambodia.
The geological structure of the intermediate neighbourhood, in so far
as it can be guessed at, under a covering of barely penetrable bush and
thick forest, is sufficiently simple. We have here a syncline of more or
less argillaceous pale Tertiary grits, between two high serrated walls of
limestone which shoots up into crags, and pinnacles, and peaks, that
show no easily apparent trace of bedding. No eruptive rocks have
been discovered, up to the present, in the valley or in the surrounding
district ; but there are quartz-veins in the grits, which undoubtedly are
in some way connected with the stanniferous deposits.
On the slopes of the foot-hills are considerable quantities of limonite,
occasionally manganiferous to a high degree, which appear to belong to
the uppermost stratum of the grits. These are but fragmentary patches,
all that has been left by erosion, of the deposit as it was originally laid
down, but it is in them that the tin-ore is found, in a finely-divided
state. Four such deposits are known, and there may be others : they
are dispersed along the right bank of the stream, but limonite has been
also observed at two points on the left bank.
The only stanniferous ore-body that has been properly studied so
far, lies a little way up stream from the village of Puntiu ; but, as all
the others have precisely the same external characteristics, it may
perhaps be regarded as typical. The limonite has been carved up by
erosion into isolated blocks immersed in sandy ore ; the tin-ore occurs
* "Gisements stannifSrea au Laos franqais." By L. Gascuel. Annales des
Mines, 1905, series 10, vol. viii., pages 321-331.
THE ALLUVIAL TIN DEPOSITS OF BANCA, BILLITON, SIAK, ETC. 53
throughout both the blocks and the sand, in the biggest fragments as in
the smallest particles. Nothing reveals its presence to the eye, except
where an especially rich morsel occurs (assaying, for instance, more than
10 per cent.). The cassiterite is, indeed, in so fine a state of division
that, with crushing and washing, only a very small proportion of it can
be retained : most of it is carried off in the sluicing. The ore is of a
red-brick colour, more or less tinged with brown : the outer surface of
the bigger blocks is brown, and where manganese predominates the
colour is darker still. Antimony and bismuth also occur in association
with the limonite, but no sulphur. The Puntiu deposit has been worked
in a nonchalant and primitive fashion by the natives, in the intervals
left by the rice-sowing and the rice-harvest, by means of roughly circular
shallow pits. Smelted in an equally primitive fashion, the ingots of tin
are purchased by Chinese merchants at Pak Hinbun, and sent off to
Bangkok. However, it is thanks to this mineral industry, such as it is,
that the natives are enabled to pay regularly their taxes, even in the
years of drought ; as to working on a large scale, by European methods,
the prospects do not seem hopeful at present. Opencast working would
not be difficult, but the ores are too poor, they occur too far away from
any industrial and commercial centre, and the means of access are still
the reverse of easy. By the quickest route, it takes twenty to twenty-
five days to reach the site of the deposits from Saigon, and that by a
mere track. For goods, the Mekong river furnishes the only possible
(but unreliable) approach.
54 )
CHAPTER V
ALLUVIAL TIN MINING.
Stream tin is harder to separate from the gravel than gold on account
of its somewhat low specific gravity. There are various methods
employed, the one most in use being the separation of the tin-ore by
means of the sluice box, which slightly differs from the one used in
gold mining. A fair stream of water is always necessary to effect good
results. The two forms of sluicing may be classified as box-sluices and
ground -sluices. In the former the gravels are lifted and placed in the
sluice-box by hand, whilst in the latter the gravel is washed into them
by water ; this method can only be used when natural facilities are
suitable. The length of the sluice necessarily varies with the quality
and quantity of the gravel to be treated, and the fineness of the tin to
"^be saved. There must also be a complete disintegration of the tin-
bearing gravels. The grade best suited to the particular gravel to be
treated must be determined by actual experiment.
A sluice-box commonly in use is about 16 feet long by 24 inches
wide at the upper end, and 22 inches wide at the lower end. Seven of
these boxes would make the tail-race a total length of 150 feet.
The Hopper-box, 8 feet long and 4 feet wide at the upper end, and
22 inches wide at the lower end, is fitted with a perforated iron plate
4 feet at the upper end, or a gridiron of steel or iron bars ; and it is
upon this that the first material is placed, and the large stones removed
by a fork. In the sluice, men are posted at intervals with shovels,
whose duty it is to push back the heavier ore against the water,
allowing the lighter material to flow away ; and it is to a great extent
upon the efficient working of these men that the amount of tin saved
or lost depends.
Within the first few feet about 80% of the tin-ore is saved,
and it is necessary, where the quantity of tin-ore to be treated is very
large, to place several men close together in the race. After this point,
one or two men walking up and down the race and stirring any masses
that may have collected at any particular point will be found sufficient.
The exact point at which it will not pay to further handle the ore can
be easily determined by direct experiment ; this is largely dependent
upon the quality and quantity of the alluvial wash to be treated and
the size of the grains of tin-ore.
A mechanical rake has been substituted in the tail-race by way of
experiment, but it was found that the loss of tin was greater by this
ALLUVIAL TIN MINING, 55
method, and did not compensate for the saving of lahour. After the
sluice is washed down the concentrates must be further cleansed by
hand ; and this is better accomplished in a separate box about 5 feet
long by 3 feet wide and 8 inches deep, with a small stream of water
about f-inch deep. The larger pieces of foreign matter can be picked
out by hand.
These impurities consist mainly of some form of iron, small pieces
of quartz, and other debris. Although this may seem a very simple
operation, the author, who has had considerable experience in the
treatment of alluvial tin gravels, has found that some men will never
be really good sluicers, for the whole operation requires most careful
watching to see that the tin is not lost. It is quite impossible to save
the whole of the tin, but the loss should not exceed from 2% to 5% of
the tin-ore saved. All clay should be eliminated as far as possible, as
it has a tendency to ball and pick up particles of tin in its passage down
the sluice.
By means of ground sluicing a far larger amount of alluvial wash
can be treated. Roughly speaking, about six times more water is re-
quired than is necessary for box-sluicing.
The inethod is to have a small stream of water running over the top
of the face, and the larger quantity introduced into the tail-race at a
lower level. As all the overburden as well as the wash goes into the
tail-race, it is necessary to have this as long as possible, with
ripples placed in it at intervals. This particular form of sluicing
can be used with advantage in a country where the seasons are
extreme, and the water supply excessive at some periods of the year and
non-existent at others, when the sun would destroy the wooden sluice-
boxes.
The precautions to guard against failure are to be quite certain that
there is sufficient fall in the tail-race, and an adequate space for the
disposal of the tailings. The sluice must also be of the dimensions
necessary for the proper treatment of the material and the saving of
the tin-ore. It is impossible to fix any exact size for the sluice and the
fall, as this depends entirely on local conditions. •
The length of the tail-race depends on the cost of construction and
maintenance, the race being increased in length according to the
returns.
Where, owing to physical conditions, the tail-race cannot be made
of sufficient length, its tin-saving capacity may be increased by the use
of drops in the race and by previously removing the coarser material.
A double sluice is sometimes used, which enables one race to be in use
whilst the other one is being cleaned up.
The following is the table given in Hydraulic Miningy by Captain
C. C. Longridge, p. 81, on " The Duty of Water " :—
" The volume of water is variously measured in sluice-heads, cubic
feet, or miner's-inches. Its moving power is proportionate to the
volume or weight of the flow, multiplied by the square of the velocity,
which in turn is proportional to the square foot of the gradient. One
cubic foot of water will weigh 62*5 lbs., and if it moves at 10 feet per
56
TIN DEPOSITS OP THE WORLD.
second will have a momentum of 625 lbs. The weight of a cubic foot
of sand is 100 lbs.
" Supposing, therefore, that a cubic foot of mixed water and sand,
consisting of two-thirds water and one-third sand, is flowing through the
sluice, the weight would be roughly 75 lbs., and the momentum at
10 feet per second velocity would be 750 lbs. Thus the density of the
current and its ability to float stones would be increased by one-fifth.
The quantity of water in sluice-heads, multiplied by a fall in inches in
a 12 feet box, gives the number of cubic yards sluiced per hour."
Example : —
Number of Sluice Heads.
Grade in Inches per 12 feet
box.
Number of Cubic Yards
Sluiced per Hour.
10 heads
12 „
6 inches
7 „
60 cubic yards.
84 ,, ,,
Conversely, the number of cubic yards required to be sluiced per
hour, divided by the fall of the box in inches, gives the number of
sluice-heads (cubic feet per second) needed for the purpose.
EXAMPLES.
Showing the number of sluice-heads needed for sluicing one cubic
yard per hour, in sluices of various grades : —
Grades.
Number of Sluice
Heads required.
3 inch
per
12 feet box
or ]
[ in
48-00
-
•333
4 „
»)
))
— 1
'■ 99
36-00
-
-250
5 „
i»
1)
— ]
^ 99
28-00
-
-200
6 ,?
11
)?
— ^
^ 99
24-00
-
-166
7 „
9«
>»
—
99
20-57
-
-142
8 „
»1
9)
— 1
^ 99
18-00
-
•125
9 „
•»
1»
— ]
*■ 99
16-00
-
•111
10 „
1»
5»
—
*■ 9?
14-40
-
•100
11 „
J»
1»
—
^ 99
13-09
-
•090
12 „
H
59
—
^ 99
12-00
-
-083
The nature of the material naturally affects the above results.
Material of high specific gravity, mixed with large quautities of
irregular stones, decreases the quantity sluiced ; whereas material of
low specific gravity, with well-rounded stones, increases the amount.
Alluvial, in fact, is more easily sluiced when it contains a fair proportion
of well-rounded stones, say, from 4 to 8 inches diameter, since the stones
keep the fine and heavier material from settling on the bottom of the
sluice. Fine heavy wash is the most difficult material to sluice.
16 feet
per
minute
30
91
39
9»
45
120
200
320
400
ALLUVIAL TIN MINING. 57
THE MOVING POWER OF WATER.
Assuming the amount of available water and the character of the
material to be known, the strength of the current required to sluice the
material has to be estimated, as on this depend the grade and dimen-
sions of the sluice. In this estimation reference may be made to the
following table, which shows the moving power of water in smooth,
straight sluices, without riffles : —
TABLE I.
begins to wear away fine clay,
just lifts fine sand,
carries sand as coarse as linseed,
moves fine sand.
„ pebbles of inch diameter.
„ of egg size.
„ stones of 3 to 4 inch diameter.
„ boulders of 6 to 8 inch
diameter.
600 „ „ - - „ boulders of 12 to 18 inch
diameter.
Reference to tables of this description, or, better stili, to actual
experience, will enable the engineer to select a rate of flow best suited
to the material.
CALCULATING A GRADE.
When the required velocity of the current has been determined,
the necessary grade for the sluice may be calculated by the following
formula : —
^ V2 X P ^
^=-2A-^^
Where b = Fall in feet per mile, which may be reduced to inches per
12 feet box, by multiplying with '027 ; or to inches per
rod (16 feet) by multiplying by "036.
V = Velocity in feet per second.
P = Wet perimeter of sluice in feet.
A = Area in square feet, filled by the water and dirt,
C = Variable co-efficient, depending on the frictional character
of the material and of the sluice-paving, and varying from
6 for light gravel, to 8 for boulders and heavy clay.
Example : — What grade in feet per mile must be given to a sluice
3 feet wide and 6 inches deep, to give a velocity of 320 feet per minute
— i.e., 5*3 feet per second, the gravel being fairly light ?
_ (0-3) X (3 + -5 + -5) _
^ = 2 X 3 X -5 ^ = 37 68 C
58 TIN DEPOSITS OF THE WORLD.
Taking C in this case as 6'o, the fall per mile will be, roughly,
245 feet ; or, multiplying by '027, the grade per 12 foot box will be
6*6 inches.
It may be noted that a lenj^^thy course of measurements at Kumara,
the largest hydraulic sluicing field in New Zealand, has shown that with
ordinary alluvial, sluiced in boxes, paved with wood blocks, the number
of cubic yards of material required to be sluiced per hour, divided by
the number of sluice-heads of water used, will give the required fall per
12 foot box.
Practically all the tin mining in the Malay Peninsula is carried on
by the Chinese — very often in the case of alluvial mining without
European supervision. The Malays are only engaged in a small way
on the easily won surface alluvial ; they also supply the timber and
firewood necessary for mining operations on contract.
Surface Alluvial is generally exploited by a system known as
*' lampan," or surface, working. Several snaiall channels are cut in a
hillside, down which the washdirt is allowed to run into a main channel,
where it is collected, and the tin .washed up in an inclined sluice-box of
a type which will be described later. Where water can be brought
round easily, continuous working is carried on ; otherwise it is necessary
to wait for rain, which is stored in pits at the top of the workings.
This is the method practised, mostly on a small scale, by the Malays,
who never engage in anything like deep alluvial mining.
A good example of working this form of deposit is to be found on
the property of the Leh Chin Mining Company, Limited, of Dublin,
at Changkat Pari, Ipoh. This company has paid dividends varying
from 5 to 15 per cent, uninterruptedly since its formation in 1891, and
is still working at a profit. The mine is 277 acres in extent, and the
system pursued by the company is leasing for short terms to Chinese.
As fast as the ground in one place shows signs of exhaustion the
coolies move a little further on. The outfit required for a gang
of coolies consists simply of hoes, rakes, baskets, and a sluice box.
The " changkols," or hoes, are of two kinds, long and short-handled.
The latter have handles 5 feet long and are for breaking down the
washdirt in situ. The handles of the former are 9 feet in length, and
these hoes are for keeping the tin alluvial in motion whilst in the sluice
box. The blade of the hoe is of wrought iron, and is made locally,
costing about 50 c. (1*. Ifc?.). It is inclined inwards, i.e., towards the
holder at an angle of about 60°. For breaking ground its dimensions
are : length, 1 foot ; width, 6 inches ; and for the sluice box it is
1 foot 3 inches long and 9 inches wide. The "ki-tsai," or wicker
baskets for carrying the washdirt from the open works to the sluice
box, are flat and of varying sizes, but 1 foot 6 inches long and 1 foot
3 inches extreme width in the middle are sizes commonly seen. They
are carried across the shoulders on a yoke pole known as the " kandur "
stick, about 4 feet long, the coolie balancing himself whilst carrying a
heavy load on each side in an extraordinary manner. At first sight it
would appear that this primitive method of transport would be both
wasteful and inefficient. Experience in the Straits has, however, shown
ALLUVIAL TIN MINING. 59
that European methods, whether by tramroads or otherwise, cannot
compete with the coolies and their baskets for economy in working
alluvial. From actual personal observation, it has been noted that a
coolie will carry a load of 80 katis (104 lbs.) a distance of 50 feet to the
sluice box, returning the same distance to the working face, in one
minute. Coolies carrying baskets work 6 hours a day, in spells of
3 hours at a time. Deducting one-eighth, probably a good deal in excess
of the actual period lost, at any rate with coolies working on contract,
a coolie will carry 15 tons per day this distance. At the average rate
of wages of 40 c. (lOjc?.) per day, this works out at 0*025 c. {id.)
per ton.
Sluice Box. — For surface working a small sluice box ("lanchut
ketchil ") is used for washing the tin dirt, in contradistinction to the
large sluice box ("laochut besar"), employed in the case of deeper
workings. The box is shaped something like a coffin, widening out in
the centre, and narrowing again towards the bottom. It is inclined
from the top downwards about 1 in 10, and has these dimensions, viz. : —
Length, 9 feet.
Width at top, 1 foot.
„ bottom, 1 foot 3 inches.
Extreme width, 2 feet 6 inches.
Water find washdirt are let into the box together through a hole
6 inches wide at the side of the box, and 1 foot from the top it. At
the widest part of the box, which is situated 3 feet from the top, there
is a ridge 3 or 4 inches high, over which the coolie, who is manipulating
the tin ore, allows the mixed water and ore to escape in a small stream.
The amount of each he regulates with a long-handled hoe and with his
foot in a very expert manner. The art of doing this is only learnt after
considerable practice, and being besides very hard work — for he must
not stop for much rest whilst ore is in the l30x — the coolie doing this
part will, by mutual consent, get rather more pay, say a few cents per
pikul, than the rest of the gang. If the washdirt contain much clay it
has to be puddled in a shallow rectangular pit at one side of the sluice
box before being washed in it. The puddlins: is done with short-
handled hoes. The tin ore is concentrated simply by being pushed up
and down the bottom 6 feet of the sluice box with the long hoe, the
action of the water leaving the clean tin at the top. As the coolies work
three hours at a time, the box is cleaned up before changing shifts,
except in the case of exceptionally rich ore, when it may be cleaned up
twice in a shift. One coolie is employed in picking out the stones from
the washdirt by hand, and with a rake. The latter, being of the
ordinary kind, needs no description. Another coolie stands at the
bottom of the sluice box wifh a short hoe, keeping the tail-race clear of
the " amang," or gangue, washed down, and seeing that no tin escapes
with it. Thus, if puddling be necessary, four men are required to work
a small sluice box, but if not, then three men only. With a sluice box
as described, 50 cubic yards (or say, roughly, 100 tons) of tin alluvial
can be washed in six hours if the ground be fairly loose. The loss of
60 TIN DEPOSITS OF THE WORLD.
tin is not nearly so great as might be imagined, and, except with very
rich ore, or careless washing, may be put down as not exceeding 3 per
cent. An assay of a fairly rich sample of tailings from the Changkal;
Pari Mine, kindly made by Mr. Benedict Kitto, showed 1*7 per cent,
of metallic tin, but, with the present system of working, the bulk of
tailings would not run so high. The tin may be said to be save! rather
by the expertiiess of the washer than by any particularly advautageous
feature which this form of sluice box possesses. It is not often that it
pays to rewash tailings. The Straits Trading Company, Limited, sell
the tailings from the sluice boxes at the Ipoh works at 40 c. per pikul
(= 14*. lOd, per ton), but in this case they are from the reconcentra-
tion of badly washed ore, and not from direct treatment of washdirt.
Working of Shallow Alluvials and Deep Leads, — The working
of shallow alluvials and of deep leads may be considered conjointly, for
the open cast system pursued is in each case the same. The over-
burden is stripped by a class of men known as "nai-chiang" coolies, so
called because they are paid for this work at a fixed rate per " chiang."
The latter has been fixed by the Chinese Protectorate at 30 feet long x
30 feet wide X 1 J feet deep = 50 cubic yards. The average price in
Kinta is $4*00 to $7-00 (8*. lOrf. to 15^. 5Jrf.) per "chiang," according
to the distance the overburden has to be removed behind the working
face. This is equivalent to 8 c. to 14 c. {2d, to 3fc?.) per cubic yard.
The men working underground, or in the open mine, breaking down
washdirt, or washing the same, may be of two classes : either " kung-
si-kung " (so called from the word " kung," meaning a day's work),
working on day's pay at fixed wages, in fact what are called in
Cornwall "owner's account." The men in this case is the "thauke" or
advancer, who may or may not be the actual owner of the mine
guarantees their pay, whether the mine prove profitable or not) ; or
" co-operative coolies," working in " kongsis," or gangs, in number from
20 men upwards. The remuneration of these latter depends upon the
amount of clean tin ore produced, being in short a modified form of
tribute with the advancer, who, if not the actual owner of the mine,
has his own separate arrangement with the latter.
The " karang," or tin-bearing washdirt, is chiefly crystalline quartz,
with some felspar ; whilst the " kong," or bed-rock, is either granite or
limestone.
Pumping. — Where water is encountered in any considerable quantity,
it is raised by a " kin-cher," substantially the same as the old Californian
wooden pump described and illustrated in Warnford Lock's Practical
Gold Mining^ p. 188. It is of similar construction to the pumps used
in China and Japan for irrigating the padi fields, and consists of an
endless chain of wooden slats, revolving round similar slats fixed on a
wooden rod, and actuated by small wheels at the top and bottom of the
same. The length of rod and chain varies, of course, with the depth
from which water has to be raised.
At Saiak Tin Mine, near Batu Gajah, Kinta, there is a pump
raising 75 feet in one lift, and this may be taken as about the maximum
capacity. The angle of inclination is usually about 30°. The wheels
ALLUVIAL TIN MINING. 61
have eight spokes, each 1 foot long x 2 inches wide X 2 inches thick.
The slats are 9 X 3 X 1 J inch. The motive power of the pump is
bupplied at shallow depths by coolies working a treadle at the top.
The barrel of the treadle is 6 inches diameter, and the spokes of the
same on which the coolies tread are 9 inches long and 6 inches in
diameter. With greater depths, where water power is available, small
overshot wheels are used, 4 feet 6 inches diameter, and 3 feet breast,
as much as one-eighth of the whole wheel being continually under water.
Chinese System of Mining, — Where the overburden is considered
too deep to be removed by an open cast working, shafts are sunk, and
the washdirt removed from them. If the ground will stand, in stiff
clay for example, they are made circular, and are 3 feet diameter. In
running ground they are 3 feet square, and are timbered with 1 inch
laths. One mine will have twelve or more of such shafts, laid out in
straight lines, and at right angles to one another. They are 18 to 20 feet
apart. The shafts communicate witb one another underground by
a series of drives. Average size of drive at commencement of extraction
of washdirt 4x3 feet. These will be continued in width and depth
until the deposit of washdirt is worked out. The roof of the drive is
supported at intervals of 3 to 4 feet by single props, 4 to 6 inches
diameter. These have semi-oval slabs at top and bottom, the fiat side
in each case being nearest to the ground.
If there be only a little water in the workings it is baled out with
the ubiquitous kerosene tin. Otherwise the workings are so arranged
as to drain into one central sump, from which the water is pumped up
through iron pipes 4 or 5 inches diameter. A centrifugal pump is then
placed in the sump, and is work<?d by steam. The washdirt, if stiff
clay, is raised in the wicker baskets already described. When too soft
for these, kerosene tins are used. The ordinary load is 1 pikul at a time.
A rough windlass is used for hoisting, such as is commonly seen with
prospecting shaft. The barrel is 6 inches diameter, and is bound with
hoop iron at both ends. According to the depths of the workings, the
windlass is either single or double handled. The handles are simply
pieces of bent stick dovetailed into the windlass barrel.
FIG. 15.— HYDRAULIC GlANT OR MONITOR.
Showing swivel connections (a) with the supply pipe, and counterweight (6), to
facilitate the directing of the giant.
62
TIN DEPOSITS OP THE WORLD.
Where it is possible to use the hydraulic monitor its services should
always be taken advantage of. This monitor or giant is used for
breaking down the ground by cutting a piece away at the bottom of the
face, which causes the upper part to collapse.
In breaking ground great care must be taken not to bring down too
large a quantity at a time, which adds to the cost of removing, and
might possibly injure the monitor and men at work. Fig. 14 gives a
drawing of a monitor with the balance arranged so that it is possible for
one man to work it in any direction without assistance.
Hydraulic elevators have been used with success in place^i where no
other means were available. To work the elevator successfully there
must be a sufficient volume and pressure of water, and the alluvial wash
operated on must not contain too many large stones.
The size of the elevator to be employed can be determined by calcu-
lation before erection.
The following table is the actual result obtained from a mine in
New Zealand : —
No. of
No. of
No. of
Ele-
Hours
Cubic
vator.
Sluicing.
Yards
Sluiced.
Height 1 Head of
Dia-
Mate- 1 Water
meter
rial is lonEleva-
of
Lifted. tor Jet.
Jet.
Diame-
ter of
Liner
on Ele-
vator
Pipe.
No. of
No. of
Sluice
Sluice
Heads
Heads
Used for
Used for
Lifting.
Sluicing.
No. 1
No. 2
No. 2a
No. 2b
Feet.
Feet.
Ins.
Ins.
2179-5
58,107-9
62-5
400-5
H
7J
10
8-75
1816-5
60,550-0
63-5
408-0
7J
12-5
11-25
1295-5 )
43,183-4
63-5
42-0
408-0
351-0
n
7i
7J
12-5)
7-5 f
7-5
I No. of
Cubic
Yards
Lifted
per
Hour.
26-66
33-30
16-66
Longridge, " Hydraulic Mining," p. 64.
The following account is given by Frank Owen of the Hydraulic
Mining in the Malay Peninsula : —
" There are two alluvial mines in Perak worked by hydraul icing s
The Bruseh Mine in the Batang Padang district, and the Gopeng Mine
in the Kinta district.
"The Bruseh Mine hold a concession of 1,000 acres, of which 600
are estimated as payable as tin-bearing ground. The mine consists of a
hillside 700 to 800 feet high, and before it was taken up by the present
owners it had been worked by Malays by ground sluicing for 40 years*
The ground is tin -bearing from surface down to a depth of 20 feet, with
an average yield of 2 to 5 katis (2*6 to 6-5 lb.) of black tin per cubic
yard. The water is brought round by a watercourse 5 miles, and down
to the working face by 800 feet J-inch steel piping 8 inches diameter,
in 6 feet lengths. The available head of water is 230 feet, giving about
100 lb. working pressure with a 2-inch nozzle. When there is a full
pressure of water the monitor is capable of breaking down 300 cubic yards
of washdirt in a working day of 20 hours. A good deal of this consists
of hard lumps of clay difficult to break up, otherwise it is estimated
55
t-4
P
Q
n
ALLUVIAL TIN MINING. 63
that 500 cubic yards of ground could be treated in the same time. The
mine, when in full work, returns 200 to 300 pikuls (11*90 to 17*86 tons)
of black tin monthly, with a produce of 68 per cent, metallic tin. As
there is sufficient water to work a second monitor, which will shortly
be erected, the output of the mine will be doubled without a propor-
tionate increase in the working cost.
" Method of Working. — The washdirt is carried down the hillside
from the working face to a series of sluices, in 120 feet of launders,
1 foot deep, beginning with a width of 1 foot and ending 2 feet 6 inches
wide. There is a drop of 48 feet from the monitor to the launders, and
the washdirt flows down a channel to the latter. The launders are
lined at sides and bottom with corrugated iron to prevent them being
worn out with rough stones, &c. The life of one of these launders,
when lined with iron, is three year.-", whilst without it they only last one
year. Bars of wood are nailed across the bottom, zig-zag fashion, to
break up the hard lumps of clay. The launders are made in 12 feet
lengths, and cost 21c. (5^d.) per foot run. At the bottom of the
launders the washdirt has to pass through a grating of f inch iron bars
2 inches apart. Any large stones are caught here and picked out from
time to time ; there is then a fall of 5 feet to the sluices, tending to
further break up the clay lumps. There are 400 feet of wooden sluices
1 foot deep with varying widths, thus : —
" First 50 feet, 3 feet 6 inches wide.
"Next 300 feet, 2 feet wide (with riffle bars 3 inches wide and
2 inches thick, placed 1 foot apart).
" Last 50 feet, 4 feet wide.
"The sluices are constructed in lengths of 10 feet, having a drop of
6 inches between each length. Over 75 per cent, of the black tin saved
is caught in the first 50 feet of sluices, where the washdirt is kept
constantly moving with hoes, in the same way as in the ordinary sluice
box. Stones are picked out with rakes.
" The riffle bars are removed when it is desired to clean out the tin
from the middle part of the sluice. The ore from here and from the
bottom 50 ft et of the sluice is re-washed in the top box. A product of
50 per cent, metallic is obtained from the sluices ; this is re-washed in a
small sluice box of the kind previously described, and concentrated by
hand jigging with sieves.
" The last 50 feet of the sluices have been widened to 4 feet with a
view to re- washing all the tin there, and thus doing away with the sluice
box. At Bruseh one man (a Malay) cleans 8 pikuls (9*52 cwt.) of
black tin per diem. The tail race is IJ miles long, 1 foot 6 inches
wide, and 2 feet 6 inches deep, and is cleaned up once in six months,
when a little tin is recovered. The total loss of tin is about 5 per cent.
The system of working is to cut down ground with the monitor for
20 hours, and then to flush the sluices with clean water, and clean up
the tin during the remaining four hours ; the latter operation is of
course done by day.
" The Gopeng Mine is situated near the town, from which it takes
its name. The area of the concession is 500 acres, the average depth
64 TIN PEPOSITS OF THE WORLD.
of washdirt 12 feet, and the yield of same about 2 katis (2*6 lb.) of tin
oxide per cubic yard* There is no overburden to be removed. There
are 2| miles of watercourse and 5 miles of J-inch steel piping 12 to
13 inches diameter in 12 feet lengths, with telescopic joints. The
monitor has a 2-inch nozzle. It is employed in cutting ground for
14 hours, the remaining 10 hours being for washing up the tin.
"The monitor works from 4 p.m. to 6 a.m., and washing up takes
place from 6 a.m. to 4 p.m. The head of water available is 249 feet,
giving a working pressure of about 108 lbs. The ground, being soft, is
broken up by the monitor at the rate of 500 cubic yards in 14 hours.
The system of washing is different to that at Bruseh. Here there are
no sluices or riffles, but simply a long ditch in which 40 Malay women
are stationed at intervals. They catch the tin dirt as it flows past them
in a wooden dish called a ' dulang,' similar in shape and size to the
South American gold-washing *batea.' They are paid 40c. (lOJc?.)
per day, and but very little tin, it is claimed, escapes in the tail race."
lent
port
lins
lese
the
has
the
to
jing
oth
'.al ;
aite
>wn
par
ing
ing
tnie
bly
K)r-
the
md
ind
ain
iiig
iud
64
of was
oxide
are 2\
13 im
monit<
U hoi
place
giving
broken
The S3
DO Sluj
are sta
iu a ^
South
per (la;
kT
6
c!^feC^
■^
( 65 )
CHAPTER VI.
TIN LODE DEPOSITS IN THE MALAY PENINSULA.
The Pahang Corporation, Ltd. — This company holds a government
lease of 200 square miles situated about 40 miles by river from the port
of Kuantan, in the Federated Malay State of Pahang.
The country has a gradual slope from the coast to the mountains
about 40 miles inland where the mines are situated ; the axes of these
mountains are granite. The general geological features resemble the
west of Cornwall, but the geology of this part of the Peninsula has
been little studied. Mr. W.^. Derrick, in a paper read before the
Institute of Mining and Metallurgy, gives the following particulars :^
" The lodes run approximately east and west, are from 50 to
2,000 feet apart, and range in thickness from 2 to 10 feet, producing
from 1 to 15 per cent, of tin oxide to the ton. The lodes underlie both
north and south, at angles ranging from 10° to 40° from the vertical ;
they have generally one well-defined wall, but seldom two. The granite
is overlaid by varieties of clay schists, with the tin lodes running down
right through the slate into the granite, a few isolated hills of calc-spar
remain, although at one time this rock must have covered the slate, as
the latter is everywhere seen intersected with veins of spar."
Mr. F. J. Stephens, in a paper read before the Institute of Mining
and Metallurgy on the same mine, writes as follows : —
" The beds of the rivers are full of boulders and gravels consisting
largely of granite and gneiss. In some cases the granite has become
decomposed over considerable tracts, forming kaolin of a remarkably
pure quality* This granite contains for the most part a large propor-
tion of felspar, but very little mica.
" Tourmaline or schorl is rarely met with,
"On the Kuantan River, some miles below the tin mines of the
Pahang Corporation, limestone occurs in great masses, white and
greyish in colour, and lying unconformably on slates and schists ; and
<;alc-spar is found in great quantity along many of the hill-tops, again
resting unconformably Upon the steeply-inclined edges of the slates.
" Massive clay-slates, imperfectly jointed, and very rarely showing
conformable cleavage, are met with, usually dipping at a high angle and
* Trans, of Inst. Min. and Met., Oct. 1898.
66 TIN DEPOSITS OF THE WORLD.
having a general N.E strike. These become schistose occasionally,
mica entering largely into their composition. They are of various
colours, but a dark blue tint predominates. Large areas of these rocks
are broken up, presenting the appearance of compact breccias. Quartz
does not enter largely into their composition, although the lodes in their
barren parts seem to be composed entirely of quartz. Cross-courses
appear very frequently in the Kuantan district ; in fact, considerable
disturbance must have occurred at some time, there being many disloca-
tions of the rocks themsefves.
" The geological structure at Sungei Lembing is so remarkably like
that of certain parts of Cornwall that the disappearance of the main
lodes in depth would be a matter of surprise ; even had I not seen the
lodes cutting the granite in the S- Kenau, I should have no hesitation
in saying that they would continue through granite if it were
encountered. Nor have I any doubt that it will be possible to follow
these lodes in granite for considerable distances, seeing that in Cornwall
similar fissure lodes have followed the granite for over 1,000 feet. The
Sungei Lembing Lodes are exceptionally rich, they are of great wddth,
and they carry over considerable parts of their course a high percentage
of tin ore.""
*The principal metals found in the lodes are tin, copper, iron, and
arsenical pyrites, blende, and galena. Of these metals tin and copper
only have been discovered in workable quantities ; the latter usually
carries from 25 to 30 oz. of silver to the ton, and appears to be quickly
giving place in depth to tin.
The mines now being worked by the Pahang Corporation were, so
report says, continuously worked by Malays and Chinese for more than
100 years, the large surface excavations made by them, some of which
are 1,000 feet long, 200 feet wide, and 150 feet deep, testifying to this
being a fact. The open-cast system was the only one adopted by the
old miners, and as timber was seldom made use of to secure loose ground,
the sides of their working were sloped or terraced to keep them from
falling in. This, and not the thickness of the lodes, accounts iu many
instances for the great width of the old workings. Under native
management (at least within recent years) the mines were not a
financial success, owing apparently to want of capital, and, conse-
quently, of proper machinery, as well as the native objection to doing
anything in the shaje of dead work, their mode of operation being to
follow any payable ground from the surface down as far as they were
able to without steam pumps and timber.
Explosives of any description were never made use of owing to a
strange superstition firmly believed in by the Chinese, viz., that the use
of explosives frightens away the metal in a mine. In consequence of
this, any very hard ground could not be worked. The ore obtained was
crushed by wooden stamps shod with iron and worked by small over-
shot and undershot water-wheels. The only dressing appliance used
was a Long-tom, the tail losses from which were very heavy. These
* W. H. Derrick, op. cit.
TIN LODE DEPOSITS IN THE MALAY PENINSULA. 67
tails were assayed, and found to contain as much as 7 per cent, of tin
oxide. They are principally composed of coarse grains of tin and
quartz adhering together, which only required finer crushing to allow
the tin to be readily separated out.
For working the mines, the Pahang Corporation made use of Chinese,
Javanese, Malay, and Tamil labour, Europeans being employed for
supervision work only. With the exception of ore dressing, all work
is let out on contract.
Stoping is paid for by the truck of 16 to 18 cwt., prices delivered at
the battery ranging from 1^. 9^?. to 6s, per ton, according to the nature
of the ground stoped and the distance of the mine from the battery,
which in some cases is as much as 2 miles, the mines being all con-
nected with the batteries by tramroads.
Contractors pay for all tools and materials, dynamite, fuze, detonators,
candles, &c., and put in timber as required.
If the quality of the ore delivered at the battery drops below a
certain percentage (which is fixed at the time of letting the contract J,
the contractor receives nothing for such ore. This insures the Company
against the delivery of waste. Each contractor's parcel of ore is stamped
separately, and is constantly sampled and assayed as it passes through
th^ mill.
Driving and sinking are let by the fathom, and prices range from
£1 10*. to £4 for drives 7 feet by 5 feet ; £2 10*. to £5 10*. for
winzes 6 feet by 5 feet; £5 to £30 for shafts 12 feet by 4 feet, these
dimensions being all clear of timber.
Contractors, as in stoping, pay for all stores and put in timber as
required, the timber of course being supplied free by the Company.
Drills are sharpened for contractors free. At one time this work was
charged for, but it was found men wasted much time by using blunt
tools rather than pay to have them re-sharpened.
The distances driven per month by a gang of six men working in
8-hour shifts vary from 10 to 40 feet according to the nature of the
ground.
Shaft-sinking ranges from 10 to 20 feet per month in hard slate,
when twelve men are employed working 6-hour shifts.
The Chinese miner makes good progress in moderate and soft
ground, but is usually a poor miner in really hard rock, and on this
account he cannot compete with white labour. If time alone was the
sole consideration in mining this might be so ; but when expense also
is taken into consideration, it is far otherwise, a fact which is very
apparent when one considers that white labour when employed on
actual mining work is about ten times as expensive as native labour ;
in other words, a White man has to drive or sink ten times the dis-
tance done by a native in order to compete with him, whereas in any
but hard ground his progress would probably not much exceed that of
an ordinary skilled Chinese miner.
The average cost of mining, including cost of drives and winzes
(but not permanent shafts), timber, hauling and pumping charges, and
European supervision, is os. per ton.
£ 2
68 TIN DEPOSITS OF THE WORLD.
The Pahang Corporatioc have a battery of 70 head of stamps.
The stamps are of the usual Calif oruian type, weigh 850 lb., and
driven at a speed of 90 blows a minute, they crush about 2^ tons per
head per day. Vertical, high-pressure, nou-condensing engines supply
the motive power.
The dressing appliances first introduced were the usual concave
and convex buddies from 12 feet to 25 feet in diameter, frames and
tossing gear as seen on the dressing floors throughout Coruwall ; but
notwithstanding the cheap labour available for working these, they
are gre,dually being replaced by more modern machinery and with the
best of results.
Frue vanners with corrugated belts, size 4 feet by 12 feet, are
found to answer well in treating the ore as it comes direct from the
stamps without classification. Working thus on ores carrying a large
percentage of pyrites, the tables give heads (containing 25 to 45 per
cent, of tin oxide) sufficiently clean to go direct to the calciner without
further handling, and with tails ranging from 3 to 5 lb. to the ton.
Three tables are employed to treat the output from 10 heads of stamps.
The heads from the vanners are much cleaner than those obtained
from the buddies, and the introduction of vanners has resulted in
a reduction of at least 50 per cent, in the quantity of raw concentrates
returned to the calciners, and, consequently, is a corresponding saving
in roasting charges.
For calcining, the ordinary reverberatory furnace is used ; and
with wood at 10^. per cord (128 cubic feet), cost of roasting, including
labour, is 4*. per ton of concentrates treated.
Tin-dressing coolies cost 18*. per month. Native engine-drivers,
carpenters, and blacksmiths £2 to £3 per month. Europeans for
supervision work, £20 to £30 per month. The total dressing cost,
which includes stamping, European supervision, native labour, stores,
and roasting charges, is 5s. 6d. per ton of stone crushed.
The standard to which the oxide is dressed always exceeds 70 per
cent, of metal, the impurities being oxide of iron, a Utile silica, and
from jS^th to ^th per cent, of copper.
The total battery losses range from 5 to 8 lb. to the ton.
Two pulverisers are employed grinding some 250 tons of coarse
concentrates per month. One froe vanner is found sufficient for each
pulveriser. Plain belt machines, belts 4 feet by 12 feet, are found to
igive good results with the fine ore from the pulverisers, returning
a very clean head, and the tails not exceeding 6 lb. to the ton when
working on concentrates running as high as 10 per cent, tin oxide to
the ton.
A separate engine is employed for driving the vanners, and a high-
level tank is used for the water supply for same, thus ensuring a
regular speed and steady flow of water — two very essential points in
the successful working of frue vanners.
Jiggers of the three-compartment type were tried at one of the
mills, but did not give satisfactory results, and were consequently dis-
carded.
ack Tin.
Value.
555
46-707
662
—
523
43-159
452
32-063
472
33-995
TIN LODE DEPOSITS IN THE MALAY PENINSULA, 69
The production of one ton of oxide, in which form tlie ore is sent-
from the mines, costs from £45 to £60, but it of course varies greatly
owing to the variable percentage of oxide in the stone treated.
Stone Crushed
Output. Tons.
1900-1 - - 26-822
1901-2 - . 22-763
1902-3 - - 25-150
1903-4 - - 27-770
1904-5 - - 24-655
Working costs are given as follows in the directors' report of the
company up to 15th December, 1904 : —
Our total working costs, including expenditure on development and
all charges, amount to $14*12 per ton of ore, as sent to the battery
after sorting and rejection of waste.
Working costs amount to $12 79 cents per ton. The value of tin
in the ore won from the mines averaged $15*96 per ton, thus showing a
working profit of $1*84 per ton.
The average price obtained for our tin oxide was $809 per ton this year.
The mill crushed and treated 22,770 tons of ore, which produced
452^ tons of tin oxide, showing an average of 1-98%, as against
25-150 tons, producing 523 tons, averaging 2-08, of the previous year.
In addition to the above, 7,600 tons were crushed and treated on account of
the Pahang Kabang, Limited, making a total of 30,370 tons of 2,240 lbs.
dealt with during the year, against 34,940 tons of the previous year.
Including European supervision, native labour, stores, repairs, and
renewals to battery, dressing plant, furnaces, etc., these amount to
$3-21 per ton.
For the journey up and down a distance of some 80 miles, the
rate of carrying stores one way and tin the other is $11-76 per ton.
Pahang-Kabang, Ltd.
Ore. Black Tin.
Output Tons. Tons. Per Cent.
1904 - - 10,950 161 1-46
1903 - - 8,530 136^ 1-60
Tin Lode Mining in Tringganu, Malay Peninsula.
The Malay State of Tringganu is on the east coast of the Malay
Peninsula, and it is in the southern district of this state, known as the
district of Kemaman, that the tin lodes worked are situated. Kemaman
adjoins the Kuantan district of Pahang, to which it is geologically
allied. The principal mine is known as the Bundi Tin Mine, situated
about 40 miles to the north of the mines, worked by the Pahang Cor-
poration, Ltd.
The Bundi Mine is held under concession from the Sultan of Tring-
ganu. A royalty of 10 per cent, is paid on all tin ore raised. There
are no other charges, whilst timber and water rights are covered by the
concession. A microscopic examination of the granite rock at Bundi
70
TIN DEPOSITS OF THE WORLD.
shows that it may be classed as a fine-grained Biotite granite ; the
geology of this part of the peninsula has not been much studied, and
the dense vegetation makes any extended examination very difficult.
The axis of the range of mountains to the west of Bundi is un-
doubtedly granite. The cap of the mountain consists of schists and
slates resting on grits at an angle of about 33°, which again rests on
granite dipping to the east at an angle of 42°. It is in a valley at the
foot of this mountain that the Bundi mine is situated. The mountain
rises about 1,500 feet above the surrounding country.
FIG. 16.— Probable Section op Bukitt Bundi.
The junction of the granite and grits is very clearly defined on the
south-west side of the mountain. Near the base of the mountain and
in the valley lie a series of metamorphic schists and slates often
micaceous and talcose, and sometimes graphitic in character. These
sediments were considerably disturbed and metamorphosed by the
granite, and at some time must have covered the granite bosses now
visible on the surface. It is at the junction of the two rocks where the
best tin ore is met with. Mr. Henwood mentions a similar feature in
the Cornish mines where the best mines are situated on the granite
margins, and the geological features of a large area about here closely
compare with that of the west of Cornwall. Lodes near the granite
bosses are generally richer in tin ore than those situated at a distance
from them.
TIN LODE DEPOSITS IN THE MALAY PENINSULA. 71
The schists aud slates here are petrologically verj like the killas of
Coruwall. Some of the rock masses are of a dark grey appearance,
owing to the amount of clear quartz present. A microscopic examina-
tion of the slate in the vicinity of the ore deposit near Glen Reef
showed the characteristic well-formed crystals of cassiterite with sharp
and rounded angles. These occur in association with axioite, the
latter showing their characteristic wedge-shaped sections. Quartz
occurs interstitially.
Intrusive basic dykes do not occur in the immediate neighbourhood
of the miue, but are to be seen in some of the water-courses near.
The rocks aod mioerals associated with the tin lodes at Bundi arc
as follows : —
Rocks. Minerals.
Granite (Biotite) Quartz Iron Pyrites
Felspar Copper Pyrites
Porphyry (Eurite) Tourmaline Talc
Schists Cassiterite Chlorite
Slates Hasmatite Muscovite.
Albite. Topaz.
Axinite. Oxides of Iron.
Biotite.
The Bundi Lode traverses the country for miles, the outcrop form-
ing quite a feature in the landscape. The strike of the lode is
15° E. of N., and it has a slight easterly underlay with an average
surface width of 40 feet. Towards the south it has been subjected to
a considerable amount of denudation, and the cap covered by clays and
alluvial detritus. Towards the north it has a heavy cap of Gozzau,
which near the surface is stained a dark red by the decomposition of
the iron pyrites.
This gozzan is only stanniferous in parts ; a considerable portion
was worked by the Chhiese iii an open cut. Some of the gozzans
returned when milled from 3 to 5 per cent, of tin ore ; the stanniferous
portion has now all disappeared.
The rich ore body at present worked at. a point on the lode known
as Glen Reef is in the schist country overlying the granite at a depth
from the surface of about \0d feet. The granite is dipping to the
south at an angle of 42°.
The ore body here has no well-defined walls, and the character of
the ore is very varied ; the deposit lies between the granite and schist
country, veins carrying the cassiterite penetrate into the enclosing
rocks for some distance, and in the miner's sense may rightly be
described as a contact deposit. The whole of the lode here is more or
less decomposed. The decomposition of the granite has formed a pure
kaolin, which carries some rich cassiterite in places.
The major portion of the lode consists of chloritic schist heavily
charged (iron pyrites and cassiterite). A microscopic examination
showed that the vein stone consisted of cassiterite crystals and chlorite;
the latter occurs interstitially in small flake-like crystals, there being no
72
TIN DEPOSITS OF THE WORLD.
quartz. This ore deposit rests on the granite, which has a southerly
dip of about 40 degrees. Intermixed with the schists occur boulders
and vehis of quartz ; calcspar is also present in small quantities.
PIG. 17.— SECTION AT GLEN REEP.
At the time of my visit in April, 1904, the portion of the lode
worked was 35 feet wide, and extended 200 feet to the south. The
battery returns were over 10 per cent. A great deal of the cassiterite
is of a fine crystalline character ; the lode narrows in width at the
lower level, which is about 27 feet wide at this point. It will probably
enter the granite at 200 to 250 feet in depth. A shaft known as
Anderson's Shaft, about 700 feet due south of Glen Reef, has been
sunk 210 feet west of the lode. A drive was started at the 205 foot
level to cut the lode. At 130 feet in the drive a small bunch of tin
ore was met with, and a winze sunk at this point to a depth of 35 feet
has disclosed an ore body which is at present not well defined. The
cassiterite here is fine and compact, and loses the crystalline appearance
of the ore at Glen Reef. A microscopic examination of a specimen
from this ore-body showed that the ore consisted of a ground mass of
quartz and felspar, the cassiterite being more finely crystalline in
character than the specimen examined from Glen Reef, This is
probably a small body of ore, with no direct connection with the main
lode. , It resembles very closely an ore-body worked in the Ben
Lomond district in Tasmania, and may better be called a massive
impregnation rather than a defined lode.
The lode at Bundi constitutes one of the best defined and richest tin
TIN LODE DEPOSITS IN THE MALAY PENINSULA. 73
lodes at preseut operating in the Malay Peninsula. Taking this lode in
conjunction with the lodes at Sungei Lembing and other places in the
Kuantan district, 40 miles to the south, and the district of Sunghie
Ayam, 20 miles to the north, goes to prove that a large tin lode
mining centre exists in this portion of the peninsula. In the distant
future when the alluvial is worked out, the lodes must form the main
deposits that will have to be depended on for the future tin supply. It
must also be remembered that vast areas of this state, and in fact all
over the Malay Peninsula (now covered with dense jungle and very
difficult of access), have yet to be explored.
The mine is well equipped with pumpini^ and winding plant. The
rock drills are worked by Malays and Javanese most successfully.
The out-put of this mine for 1906 was about 20 tons of black tin per
month.
The mine gives employment to 500 men in all, 120 Javanese and
240 Chinese, who do most of the mining and surface work, and
200 Malays who are largely employed in cutting timber for fire wood
on contract at $3 per cord, delivered at the mine.
The rate of wages does not materially differ here from the rest of
the peninsula :
Chinese carpenters $la day.
Chinese miners 70 cents a day,
Chinese contract coolies - - - - 50 ditto
Engine drivers - - - - - 70 ditto
Battery and dressing-sheds men - - 65 ditto
The whole work is carried on by means of European supervision, a
European being always treated with respect. The climate, though hot,
is healthy.
The Kemaman River affords means of communication with the
coast, a distance of about 45 miles, the freight up and down averaging
£1 per ton, and the mines have a small railway to the river, a distance
of 4 miles, operated by a locomotive.
Another concession called Sunghie Ayam is worked bj*^ Chinese
about 12 miles to the north of Bundi. Here a small lode carrying some
rich tin in places is being mined by the Chinese without European
supervision. The lode is very flat, following the granite at an angle of
33°. The method employed is to stope the rich ore by means of
parallel drives, and the timbering would not disgrace a European
miner. The ore is first burnt, and then crushed by hand stamps and
roughly dressed by sieving and streaming the ore in a sluice box.
There are some big alluvial flats near the river which are worth
prospecting, as the water proved too heavy for the Chinese methods of
working. Tin is found up the coast by the Malays and Chinese for
over 100 miles north, and the writer is of the opinion that this part of
the Malay Peninsula is destined to become the Cornwall of the East for
lode mining.
74 TIN DEPOSITS OF THE WORLD.
Extract from report on the Tin Deposits of Taiping^ Malay Penin-
sula — hy Geologist to the Federated Malay States, 1904.
Ob^ tlie actual occurrence of mineral lodes there is little to be said.
Two have been worked for tin, one at Selama, the other at Blanda
Mabok. Of the direction and extent of the former I have as yet been
unable to get any information ; but close to an open shaft in the jungle
I was shown some of the debris that had been brought up, and found it
to be silicitied sandstone. From a specimen in the Taiping Museum it
is evident that the ore was very coarse. The report quoted above gives
no direction for the Blanda Mabok lode. This contains cassiterite in
coarse crystals, silver-lead as galena, which was also worked, and 2 dwts.
of gold to the ton. I may mention that I cut a section from a specimen
taken from a dump of the wall of the lode, and found that it was com-
posed of fine-grained quartzite, containing brown tourmaline in the
ground mass, and parallel bands composed of brown tourmaline, iron
pyrites, calcite, and quartz. One other specimen that I collected showed
that there had been brecciation of the wall of the lode.
The bulk of the alluvial tin was certainly derived from the granite.
For present purposes, however, it is necessary to go somewhat more
into details on this question. It has been suggested that possibly some
of the cassiterite crystallised out together with the minerals forming the
pegmatic and tourmaline granite, a suggestion perhaps warranted by the
peculiar alluvial tin deposit at Ayer Kuning ; but I have as yet seen no
indication of this having taken place to such an extent in the Taiping
range as to warrant a search for payable deposits of such a nature. The
chief source of tin has been the small fissures which were formed either
after the pegmatite had consolidated, or wl)icli had not been reached by
the residual when it was first irrupted. These fissures, which from the
specimens in the Taiping Museum appear to have been chiefly in granite,
were formed as a result of the cooling of the exterior of the granitic mass ;
and there is reason to suppose from the mode of occurrence of such fissures
in the tin districts of Saxony and Cornwall that they do not extend for
any great distance into the granite. In the Taiping range it would
probably be found, if the vegetation permitted, that over certain areas,
perhaps restricted now on account of the denudation that has taken
place, there is a network of these fissures, filled with quartz and bear-
ing coarse crystals of cassiterite. Such a network constitutes a stock'
werk, the typical occurrences of which are in Saxony.
The specimens from Waterfall Hill show that greisen has been pro-
duced on the sides of the fissures, and there is an abundance of micaceous
pebbles of a similar nature in the mines ; therefore I have no doubt that
the chief source of the alluvial tin was a stockwerk similar to those in-
Saxony. How much has been denuded, and how much has been left,
cannot be told without a minute examination of an enormous area of the
hill-sides ; but it would be indeed strange if it had been entirely washed
down into the plains. Judging from Saxony, this stockwerk should
prove worth working in situ ; but the work would have to be carried on
on a large scale and with a big modern plant ; for it may be taken for
TIN LODE DEPOSITS IN THE MALAY PENINSULA. /O
granted that if there is any tin in the rock interveninoj between the veins
it is very finely dissemitiated, and that in the veins themselves is bunchy.
Some of the veins may contain enough tin to be worked singly at a small
profit ; but it must be borne in mind that at a moderate depth such a
vein must be expected to disappear entirely.
This leads to the question, are there any deep lodes in the granite or
in the shale and sandstone series ? Now the existence of tin lodes of
any magnitude in a stanniferous area depends on the presence of faults
which allowed of the passing of the tin-bearing media, which means
that they must be faults of some size. Such faults in the granite must
have been formed when the granite was cooling, and before the ejection
of the tin from below. In the granite I have seen no evidence of the
existence of such lodes, but I do not wish to assert that there is no chance
of their being found. In the shale and sandstone there are three, that
at Selama, the Klian Besar lode at Kurau, and the Blanda Mabok.
The Blanda Mabok lode presents several points- of interest. In the
first place, the association of tin, galena, silver, and gold, is exceptional.
The lead appears to represent the copper of the Cornish lodes. Again,
all the specimens I have seen from this lode show the cassiterite to be
very coarse in grain ; and it is known from Mr. Leonard Wray's report
that it occurs in bunches. Also there is evidence of brecciation of the
walls of the lode, and of the action of boron on these walls in the pre-
sence of tourmaline. The presence of tourmaline in the walls of the
lode shows that its formation was connected with the granite intrusion,
and that it became a lode approximately at the same date as the forma-
tion of the stocktverk. The brecciation shows that it is a fault fissure
filled by the tin-bearing media from the granite, which, of course, in-
volves a connexion of the fault with the granite mass either in depth or
laterally, and gives some reason for supposing^ that the lode may be con-
tinued into the granite. In fact, but for the curious association of
minerals, this would pass as a Cornish tin lode, and such a lode would
be expected to prove rich in depth. There is another point which may
be mentioned. Among Cornish miners there is a saying that as you go
down in depth on a lode the tin gels finer in grain. Again, in many
Cornish lodes copper ore is, or rather was, abundant in the higher levels,
but was found to give way to tin in depth. Assuming, then, that I am
right in considering that the galena at Blanda Mabok occupies a posi-
tion analogous to that of the coj per in Cornwall, the lode should be
richer in tin in depth. If, then, the direction and underlie of the lode
were accurately ascertained and a shaft sunk to strike it at 50 fathoms,
all the evidence leads me to believe that good tin ore would be forth-
coming, which, if the prices of tin and labour were favourable, would be
welcomed in Larut when the prospects of alluvial tin mining are
waning.
Another question is, is there any prospect of finding a system of
lodes roughly parallel to one another in the shale and sandstone series
here like that in the killas of Cornwall ?
Petrologically, the killas of Cornwall is very like the shale and sand-
stone series ; but that is no reason why the latter should also contain a
76 TIN DEPOSITS OF THE WORLD.
system of tin lodes. The existence of such a system depends on the
state of the rock into which the granite was intruded. Now, in Corn-
wall, there is evidence to show that before the granite was intruded the
killas had been subjected to enormous disturbances, so that when the
earth movements connected with the granite intrusion commenced, they
operated on a country already crushed and therefore more susceptible to
the formation of faults than a country which had not been disturbed
since its deposition. On the other hand, the shale and sandstone series
shows much less evidence of disturbance than the Cornish killas, and it
is my opinion that before the Taiping granite was intruded no earth
movements of any importance had disturbed the series since its deposi-
tion. The probability of finding a big system of lodes like that in Corn-
wall is ihen remote ; and this makes it extremely important to lose no
time in collecting every available scrap of evidence leading to the loca-
tion of such lodes as do exist. Even if such evidence consisted of nothing
more than the discovery of sulphides, it would be of value, for lodes con-
taining sulphides apparently alone on the surface might reasonably bo
expected to contain tin in depth. A time will certainly come in Larut
when the alluvial tin will be worked out ; and then miners, unless they
desert the district, will be faced with the alternative of working the
stockwerk and lodes, or the tailings from the alluvial mines. It is not
necessary to point out of what immense value data such as those indi-
cated would be under the circumstances.
In the Malay Peninsula stanniferous cement deposits occur at Bukitt
Ebu near Kernai, on the south side of the range, and Dreda and Goa
Tumbus in lalor on the north side. In appearance these cement deposits
resemble a siliceous bog iron, and have been formed by the disintegration
of granites containing the tin ore. Near the granites occur large bodies
of pyrites ; the iron from these pyrites has cemented the small grains of
quartz with the tin stone into a compact mass. The method of mining
employed by the Chinese is to break it out and to crush it by means of
foot stamps. As one would expect from its nature, it is of very unequal
value.
French Mining Company at Lahat.
This Company has opened up what may be termed a lode. The
lode is 8 ft. wide with a NE-SW. strike, and dipped at a steep angle to
the west. It was composed of an intimate mixture of red iron oxide
and cassiterite with a little iron and copper pyrites, the gangue being
calcite and limestone, while there were some very large and beautiful
crystals of calcite on the hanging-wall. The walls were fairly well
defined. The granite contact was a mile to the west of the mine. The
ore carries about 20 per cent, of tin. In Kinta these deposits have not
lived down ; at Lahat 35 feet has been sunk with good results.
The average output of tin F.M.S. from lodes is about 1*4 per cent,
of the total produced.
CHAPTER VII.
TIN DEPOSITS OF NEW SOUTH WALES.
*In the beginniDg of 1872 public interest in New South Wales was
aroused by the accidental discovery of tinstone, by the Messrs. Fearby,
at Elsmore, near Inverell. Mr. Clegborn, of Uralla, had sent the
Messrs. Fearby to prospect the creeks of this district for gem-stones, the
best localities for which were pointed out to them by au old shepherd
on Newstead Station, named Wells. Mixed with a number of sapphires
and other gems, in the gravels of the creeks, was a heavy black mineral
in water-worn grains, which the Messrs. Fearby, supposing to be tin-
stone sent to Sydney to be assayed for tin. The result of the assay
proved that this black mineral was oxide of tin, and, the discovery
becoming known, Baron and Moxham, and other capitalists, took up the
ground near the present Elsmore Mine. Then commenced the rush to
the New England Tin-fields. The stream tin under the title of "black
sand " had been long familiar to gold-miners in New England, at Oban,
and elsewhere, where its weight, rendering it difficult of removal from
the sluice-boxes, had caused it to be regarded as worse than a nuisance.
As knowledge of its value spread, eager prospecting led to its presence
being proved over wide areas — areas which have been constantly
extended since this discovery of tin at Elsmore, in 1872, until the
latest finding of tin at Gumble, near Molong, in 1885. . . . Vegetable
Creek is only 34 miles distant, in a direct line north -north-east from
Elsmore, so that at the time when prospecting for tin was being so
vigorously prosecuted in its neighbourhood, it was impossible for such a
rich stanniferous area to remain long unknown ; and in March, 1872,
Thomas Carlean first discovered stream tin here, near the source of
Vegetable Creek.
Mode of occurrence. — Its mode of occurrence is somewhat analogous
to that of gold, dnd in a very considerable number of instances detrital
gold and cassiterite are found in the same alluvial deposits. The
principal deposits of tinstone are : —
(1) Recent and Pleistocene Alluvials.
(2) Tertiary alluvial deposits (Deep leads).
(3) Lodes.
(4) Stockworks.
(5) Impregnations.
~ * " The Mineral Resources of New South Wales," by Ed. F. Pittman, Govern-
ment Geologist, published by Mines Department, 1900.
78 TIN DEPOSITS OF THE WORLD,
The two first-named deposits are the sources of most of the tin
hitherto obtained in the Colony.
Receiit and Pleistocene alluvial deposits, — The principal stan-
niferous deposits occur in New England, in the Inverell andEmmaville
Districts. As already stated, they were first worked at Elsmore, near
Inverell, in 1872. In -this locality the tinstone occurs as crystals
dissemiuated through greisen, a crystalline granular rock consisting of
quartz and mica. The tinstone is not, as a rule, in sufficient quantity
in the griesen to render the latter a payable ore, but the gradual de-
composition of the exposed portions of the rock has set free the crystals
of tinstone, and these have been concentrated by the action of the rain
on the hillsides into a surface alluvial deposit. Considerable quantities
of tinstone were obtained from these surface deposits at Elsmore, and
at the present time, especially after rain, crystals of the ore can be
picked up on the surface. The tin in these deposits is associated with
some wolfram, and also with carbonate of bismuth. The wolfram is
derived from lodes which are known to intersect the greisen, and some
of which are occasionally 18 inches or more in width. The tin, how-
ever, does not appear to occur in this locality in the same lodes as the
wolfram.
Surface deposits very similar to those at Elsmore were extensively
worked at Xewstead, about 4 miles farther east, immediately after the
discovery of those just alluded to ; and as the mining population, which
had been attracted to these fields, spread out in their efforts to prospect
the ueighbouring country, Post-Tertiary tin-bearing alluvial deposits
were found in the creeks and gullies at Stannifer, Tingha, Stan-
borough, and other places in the district. These deposits, being
shallow, have for the most part been worked out, in fact most of
them have been worked over several times by Chinese miners, who
possess more patience than Europeans, and are satisfied with smaller
profits.
The alluvial flats along the creeks traversing granite country in this
district are all tin-bearing, but as these are of considerable depth, up to
20 feet or more, the stanniferous deposits require stripping, and are
therefore not so easily worked. The bed of Cope's . Creek was rich in
tin ore from its source to its junction with the Gwydir River, and along
its banks the Pleistocene alluvials were also a source of wealth to the
tin-miners.
A. Recent alluvial 8 feet thick, with 2 feet of washdirt.
B. Pleistocene drift 16 feet thick, with from 1 to 6 feet of washdirt. C. Granite.
Fig. 18.— Section op Stanniferous Alluvials at cope's Creek.
(After 0. S. Wilkinson.)
NEW SOUTH WALES, 79
A company has recently been formed for the purpose of working the
stanniferous gravels in the bed and banks of Cope's Creek by means of
a centrifugal pump dredge. The area acquired by the company extends
down the creek for a distance of about 3 miles below the township of
Tingha ; very large quantities of tin were extracted from it by box
sluicing in the early days of the field, and a certain number of Chinese
have obtained a living by re-working portions of it for many years past.
The operations of the company will be watched with interest, as this
will be the first attempt to recover tin ore by this method of mining.
Middle Creek, which is four or five miles to the north of Cope's
Creek, and flows into the Mclntyre River, was also extensively worked
for alluvial deposits of tinstone.
Sandy Creek, to the south of Cope's Creek, flows into the Gwydir
River. Some tin ore is said to have been obtained from this creek near
its mouth, but all attempts to prospect its bed for a considerable dis-
tance below its source were ineffectual owing to the presence of strong
bodies of water in the sands. It is probable that dredging would be an
effective method of overcoming this difficulty, and as this creek drains
similar country to that traversed by Middle Creek and Cope's Creek,
there appear to be fair grounds for believing that profitable returns
would be obtained.
At Emmaville, where tin -mining was commenced very soon after
the opening of the mines in the Inverell District, the most productive
Post-Tertiary deposit was that known as the Vegetable Creek leadJ^
Shallow alluvial deposits of Post-Tertiary age have been worked
for tin in no less than twenty-seven localities in the Emmaville District,
with more or less successful results. In the parish of Muir, masses or
nuggets of black tin-ore were found close to the surface ; the largest
of these weighed thirty-two pounds.
Tertiary alluvial deposits (Deep Leads). — The tin-bearing greisen,
the disintegration of which produced the rich surface deposits of tin-
stone, already alluded to, at Elsmore and Newstead, was also under-
going decomposition during early Tertiary times, and as a consequence
of this large quantities of stream-tin were deposited in the valleys
which received the drainage of this country during the Eocene period.
The stanniferous deposits were covered with a considerable thickness
of alluvium, consisting of gravel, sand; and clay, and containing leaves,
nuts, branches of trees, and large logs, all of which are now preserved
in a fossilised state. Eventually the valleys were invaded by streams
of molten lava, so that they have since been protected from denudation
by a considerable thickness of basalt.
The country intersected by these deep leads consists of hard bluish-
grey claystones of Carboniferous age, and areas of intrusive granite
and greisen. There are also numerous intrusive dykes of eurite, diorite.
* Much of the following information in regar«l to the Emmaville tin deposits
has been obtained from Professor David's memoir on the " Geology of the Vegetable
Creek TiA-Mining Field.'*
80 TIN DEPOSITS OF THE WORLD.
and basalt. Frequently on the higher ground are found deposits of
Tertiary -volcanic ash, which now consist essentially of the mineral
bauxite.
The Elsmore Valley Lead, about ten miles south-east of Inverell,
was, in the first instance, prospected by a bore. At a depth of 187 feet
a bed of wasbdirt, 10 feet 6 inches in thickness, and estimated to yield
15 lb. of stream-tin per load, was intersected. At a depth of 201 feet
6 inches another bed of wasbdirt, 18 inches thick, and containing at the
rate of 100 lb. of stream-tin per load, was met with, and 2 feet below
this was a third deposit of wasbdirt 1 foot thick. This lead is now
being worked by the Elsmore Valley Tin-mining Company, whose main
shaft is 225 feet deep. The deposits of stanniferous wasbdirt are
found to vary considerably in thickness, and occasionally the two lower
beds intersected in the bore unite, while in other places they are
separated by several feet thick of sand and clay. The yield of tin is
also variable, but it is stated that the average contents are about 100 lb.
of tin per load, and the mean thickness of wasbdirt is about 2 feet
6 inches. The tinstone is said to be of good quality, assaying from 76
to 77 per cent, of metallic tin when cleaned, and contains only a trace
of wolfram.
The only mine opened on this lead is that of the Elsmore Valley
Tin-mining Company, and comparatively little work has been done
there, so that very little is known as to the extent of the deposit, and in
view of the receat advance in the price of tin there is plenty of room
for further development.
The Newstead Lead, — This lead was traced from surface deposits
of tin-ore on the slope of a greisen range, and was found to deepen
gradually as it was worked northwards, until, at the spot where it
passes under Newstead Creek, Cody's shaft had a depth of 70 feet, and
some hundreds of tons of tin-ore were extracted from this claim. The
Newstead Company put down two shafts north of Cody's claim, and
very rich deposits were worked from the first, which had a depth of
130 feet. The lead is said to have an average width of 140 feet.
There is every reason to believe, especially in view of the enhanced
value of tin, that there are payable deposits of ore liere, which only
require capital for their development. There is a number of other Tertiary
tin-bearing leads in the Inverell District, such as The Donegal Lead,
Dick Jones' Lead, Brickwood^s Lead, M'Millan^s Lead, Standard
Lead, Jealousy Lead, Walmsley^s Lead, The United Lead, 4'C.
Near the junction of Cope's Creek with the Gwydir River are
several isolated basalt capped hills marking the course of an old Tertiary
river-bed which once flowed approximately parallel with the Gwydir.
Under the basalt is a considerable deposit, 14 feet thick in places, of
well water-worn quartz pebbles, with large boulders of decomposed
granite. This alluvial drift rests on a granite bottom, and is at the
present time being worked for diamonds, which occur in considerable
quantities, but of small size. The diamonds are accompanied by topaz,
sapphire, zircon, tourmaline, ilmenite, magnetite, spinel, pleonaste, &c.,
and the wasbdirt contains, in addition, up to as much as 15 lb. of stream
NEW SOUTH WALES. 81
tin per load. Although the tin is not, therefore, in sufficient quantity
to render its extraction, per se, profitable, it forms a bj-product, the
value of which goes a considerable way towards covering the cost of
•extracting the diamonds. The gems just enumerated are also found
associated with the stream tin in Cope's Creek, and many of the other
watercourses in which stanniferous deposits have been worked in the
Inverell District. With the exception of the diamond, however, none
of them is of any commercial value.
In the Emmaville or Vegetable Creek District the Tertiary alluvial
deposits have been divided into two classes, viz. (a) those which are
-capped by Tava ; and (b) bare deposits, or those from which the cap of
lava has been removed by denudation. Examples of the latter class
occur at Scrubby Gully, Surface Hill, Ruby Hill, and Y water-holes.
The deposit at the Y water-holes is by far the most important of this
olass. It has an area of about 1,100 acres, and its depth averages
about 20 feet. The alluvial deposits of clay and sand show charac-
teristic current bedding. The ore is richest at the base of the beds,
while the surface deposits contain more stream tin than the intermediate
beds, owing to their having received the ore from the sluicing of a
oonsiderable thickness of sands which at one time overlay them, but
which have since been removed by denudation. There is no evidence
of the concentration of ore in old channels in this deposit, and it is
therefore probably of lacustrine origin.
The following are the principal basalt-capped Tertiary leads which
have been worked for tin in the Emmaville District : —
1. The Vegetable Creek Lead^ including the basaltic country to
*' Kangaroo Flat," "Hall's Sugarloaf," " Paddy's Sugarloaf,"
and " The Surprise."
2. The Graveyard Lead.
3. The Springs Lead,
4. Rocky Creek Lead.
5. Ruby Hill Lead.
(>. Wellington Vale Lead.
Of these, the Vegetable Creek Lead has proved to be by far the
most important, and there can be no doubt that in early Tertiary times
it formed the main drainage channel of this country. In portions of
its course there Avero two distinct Hows of lava, an older and a newer,
■each covering a bed of stanniferous washdirt. Up to the year 1886 the
produce of these latter was 6,000 tons of stream tin in a distance of
2 miles 30 chains. At one place an area of 5^ acres of gravel, having
An average thickness of 3 feet, yielded 2,000 tons of tin-ore. The main
direction of the lead was west, and its width varied from a few feet up
to, in one instance, as much as 400 feet. The thickness of the deposit
of washdirt was occasionally as much as 14 feet ; but its average was
about 3 feet. Blank spaces were occasionally found in the lead where
the fall of the old river-bed was steepest, owing to the tin-ore having
been washed down to where the bottom was more level.
82 TIN DEPOSITS OF THE WORLD.
The Vegetable Creek Lead had two main feeders or tributaries, viz.,
the old Bose Valley Lead and Fox's Deep Lead,
The Graveyard Lead is south of, and approximately parallel with,
the Vegetable Creek Lead, and the two leads probably junction about
six miles west of Emmaville. A considerable amount of basalt-covered
country runs from this point in a northerly direction through Kangaroo
Flat to Avoca and the Fishing Grounds, and, as stanniferous drift has
been worked at these places at a sufficiently low level to allow for the
average fall of the old river valley, it is probable that the main lead
will ultimately be proved for a distance of at least 15 miles, though it
is scarcely probable that the tin-bearing wash dirt will be found to be
continuous ; on the contrary, it is much more likely that stretches of
unproductive alluvial deposits will be encountered, where the old river
has intersected country which is not tin-bearing.
The greatest depth from the surface at which a deep lead in the
Emmaville District has been worked is about 250 feet. In Wesley
Brothers' mine, at the junction of Fox's Deep Lead and the Vegetable
Creek Lead, the shaft, after passing through several distinct flows of
basalt, penetrated a layer of gravel at 247^ feet from the surface. This
gravel also rested on an eroded surface of basalt, so that there is a
possibility of another nlluvial gutter occurring at a still greater depth.
The Wellington Vale Lead, — The head of this old Tertiary alluvial
deposit is situated at a locality known as The Nine Mile, to the norths
west of Deepwater. Rich shallow deposits of stream-tin have been
worked here along a flat trending from the south-eastern slope of
Battery Mountain ; but after being followed to the east and north-east
for about a mile, they were found to dip below the basalt, a narrow strip
of which extends southw^ards for some miles, forming a covering to the
Wellington Vale Lead, No shaft has ever been bottomed in this
alluvial deposit under the basalt, although a number of attempts have
been made to prospect it. The cause of failure in each instance has
been the quantity of water met.
The geology of Emmaville is, in most respects, very similar to that
of the country round Inverell. The oldest sedimentary rocks are the
bluish-grey claystones of the Carboniferous period, and these have been
intruded by tin-bearing granites, and by quartz, felsites, and diorites.
There was a great amount of volcanic activity during Tertiary times, aa
is attested by the sheets of lava, and deposits of volcanic ashes. These
latter occupy an area of nearly 12 square miles, and they vary in
thickness from a few feet up to 40 feet. The beds consist at the
surface of a red dusty soil, and pass downwards into red, yellow, or
grey tuffs, and compact pisolitic rock containing a variable percentage
of alumina and peroxide of iron ; these in their turn graduate into
rotten spongy basalt. These ash deposits consist essentially of the
mineral bauxite, and will doubtless be of considerable value in the
future for the manufacture of the metal aluminium.
At Bailey's Mine, Rose Valley, there is an extremely interesting
occurrence of a stanniferous alluvial lead overlaid by a felspar-
porphyry lava. This occurrence was first recorded by Mr. S. H. Cox,
NEW SOUTH WALES.
83
and is the only known instance in Australia of a lead covered by an
acidic lava. (Journ. R. Soc. N.S.W., Vol. XX., Ib86, p. 105.)
9y^9Py^y/y / // . y?f//. . // yYfy^^y ///////.
W^^TT^^^^^
A. Felspar porphyry. B, Tin wash. C. Felspar porphyry-
FIG. 19.— SECTION ALONG PROSPECTING DRIVE IN BAILEY'S MINE.
(After S. H. Oox.)
Bailey's Mine is situated on the junction of intrusive felspar porphyry
with the Carboniferous clay stones, and the floor of the lead is forme<l
sometimes of the one rock and sometimes of the other, in different part*
of the mine. It is probable that the acidic lava covering the washdirt
was nearly contemporaneous with the basalts which are found overlying-
the other deep leads in the district, and represented the earlier products-
of the volcanic eruptions.
Associated Minerals, — The following minerals are found associated
with the stream tin in the Emmaville deep leads, viz. : — Magnetite,,
ilmenite or titaniferous iron, tourmaline, spinel (pleonaste), quartz, topazy
zircon, sapphire, and beryl (emerald).
Tin-hearing Lodes, — The stanniferous lodes in the Inverell and
Emmaville Districts comprise (a) Fissure Veins, {h) «Toint Veins, or
those following joints in the granite or felspar porphyry, and (c) Pipe
Veins. The veins are found most frequently in the granite, and they
occur almost exclusively within a distance of about a mile and a half
of the junction between the granite and the claystones. Professor
David states that in the Emmaville District —
76 veins are enclosed in granite.
8 „ „ „ quartz porphyry.
3 „ „ „ porphyroid.
3 „ „ „ claystone.
He also noted that out of seventy-seven veins in this district in which
tinstone occurs, nineteen consist of quartz and tinstone only, and eight
of felspar and tinstone only ; also that sixty-nine veins contained quartz,,
twenty-nine contained chlorite, and twenty contained felspar. The
following minerals also occur in different veins in the district, viz.,
mica, mispickel, iron pyrites, fluorspar, tourmaline, wolfram, zincblende,
galena, copper pyrites, bismuth, molybdenite, vesuviante, stilbite,.
hematite, pyrrhotine, manganese, scheelite, and beryl.
F 2
«4
TIN DEPOSITS OF THE WORLD.
Strike of Lodes. — The average strike of fifty-four right running
T-eins was found to be N. 39° 15' E., the range of strike being from
N. 240 E. to E 200 N.
Dip. — The average dip of thirty-seven veins observed was 77°.
33 veins dip north-westerly.
10 „ „ south-westerly.
3 „ are vertical*
Those veins, or portions of veins, which most nearly approach the
vertical have, so far, proved the richest.
Length. — The greatest length for which a vein has been proved to
be tin-bearing is about one mile.
Width. — The average width of sixty -nine veins is 1 foot 6f inches.
The six largest veins hitherto worked have the following thicknesses,
viz. : —
No. 1 Ottery vein - - - 3 feet.
No. 2 Ottery vein - - - 4 „
Butler's vein - - - - 3 feet 2 inches.
No. 1 Dutchman's vein - - - 4 „
No. 2 Dutchman's vein - - - 3 „
Curnow's vein - - - - 3 „
The majority of the other veins are narrow.
The ore in most of the stanniferous veins occurs in chutes, which
are inclined more or less steeply from the horizontal, and obliquely
along the plane of the lode. The average length of the six largest
FIG. 20.— SECTION SHOWING CHARACTER OP BUTLER'S VEIN, EMMAVILLE DISTRICT.
(After T. W. E. David.)
chutes observed was 100 feet ; average width 1 J feet ; average depth
6 feet ; average dip 26° ; average horizontal distance between chutes,
about 80 yards ; vertical distance between chutes, 50-90 feet. Eleven
chutes were observed to dip north-easterly ; two chutes were observed
to dip south-westerly.*
^ T. W. E. David—" The Geology of the Vegetable Creek Tin-mining Field."
NEW SOUTH WALES. 8$
Stanniferous pipe veins are a peculiar feature of both the Emma-
ville and Inverell Districts. They occur in granite as a rule, and are
cylindrical or oval in form. They sometimes dip at a considerable
angle ; at other times their course downwards is vertical. They do not
often extend to any considerable depth, thinning out at about 30 or 40
feet. They are occasionally as much as 4 or 5 feet in diameter,
and within these limits the tinstone occurs disseminated through
a gangue of felspar, quartz, and chlorite. Several of these pipes,
or " shoots " as they are termed by the miners, are at the present time
being worked in the vicinity of the Nine Mile ; they are all very
similar in their mode of occurrence, the chief difference being in the
diameter of the deposit. The following particulars of one of them may
be quoted : Messrs, Crocket and Knight's tin-bearing pipe vein is
situated in granite country on the bank of the Bark Hut Creek, about
12 miles north-west of Deepwater. Where originally found the pipe
vein was nearly horizontal and had a southerly trend ; it was about
3 feet in diameter, and in a distance of a few feet it yielded 8 tons
of tinstone, when it thinned out to an inch or two in diameter, and was-
abandoned. Subsequently, when tin had risen to a better pricC; the
present owners started to reopen the deposit, and soon found that it
increased in diameter and assumed a vertical course. It was followed
down for about 15 feet, having a diameter of about 2 feet 6 inches, and
then gradually became horizontal again. The excavation now measures,
about 40 feet from the surface, and the deposit has forked or divided
into two pipe veins, each of which is about 9 inches in diameter. The
proprietors have taken out about 4 tons of tinstone since reopening the
deposit, so that the total yield has been 12 tons up to the present. The
gangue consists of green felspar, and crystals of cassiterite thickly
disseminated through this. The average yield of the ore is 10
hundredweight of tinstone per ton, and the tinstone contains from 75 to
76 per cent, of metallic tin.
Stockworks. — Minute veins of tinstone occur in quartz porphyry or
felstone in many places in the Emmaville District, forming what are known
as stockworks. The minute veins appear in many cases to follow joints,
which cross one another in several directions in this intrusive rock. They
have not, so far, proved payable to any considerable extent.
Impregnations, — Allusion has already been made to impregnations
of tinstone in greisen at Elsmore and Newstead, in the Inverell District*
At Pheasant's Creek, to the east of Glen Innes, some extremely rich
deposits of tin-greisen have been found, but these were limited in
extent. Impregnations of tin-ore are also found alongside joints in
the granite in the Emmaville District, and the pipe veins already
described might also be considered to belong to this class of deposit.
The Ottery Tin-lodes, — These lodes are situated about two miles to-
the north of the village of Tent Hill. There are at least five distinct
lodes, and they occur intersecting dykes of hornblendic granite and
eurite, within a distance of a few chains from the junction line of these
intrusive dykes with the Carboniferous claystones. The lodes strike
north-east and north, and their dip is towards the north-west and west^
S6 TIN DEPOSITS OF THE WORLD.
at HDgles varying from 30° to 80°. One of these is the only stanniferous
lode at present being worked in the vicinity of Emmaville, though
others are being worked by small parties of miners in the neighbourhood
of Torrington and The Nine Mile. As mining operations have been
carried on in connection with the Ottery lode for more than sixteen
years, a brief description of the deposit may not be out of place.
The outcrops of all the Ottery lodes consist of ferruginous gossany
quartz containing tinstone, and may be traced on the surface for a
considerable distance in a south-westerly direction towards the head of
the old (Pleistocene) Vegetable Creek Lead^ and there can be very
tittle doubt, therefore, that the extremely rich deposits of stream tin
which were recovered from those shallow alluvials were derived from
the denudation of portions of the Ottery lodes, and from stockworks
occurring along their line of strike.
The oxidised or gossanous portion of the lodes extends to a depth
of from forty-five to seventy-five feet, and in the worked out portions of
the mine the walls of the shafts and drives within this zone are quite
^reen with an efflorescence consisting of sulphate and arseniate of iron.
Below the zone of oxidation, the ore passes into compact mispickel and
quartz, containing tinstone. In some places the lodes are character-
istically banded ; in others the mispickel is quite massive. The main
lode has been worked at the surface for a length of about 1,000 feet,
and at the 230-feet level it has been worked for a length of about
750 feet. In two places the upper portions of the lode have been
removed by open cuts, and there are also three shafts, the two deepest
of which are 300 and 350 feet respectively, measured on the underlie.
On the top of the hill, near the most southerly shaft, a lump of tinstone
was found weighing 2 cwt. 1 qr. 24 lb., and assaying at the rate of
72 per cent, of metallic tin. At a depth of 50 feet from the surface a
shoot of ore was met with which dipped northerly at an angle of about
20^. This shoot was 90 yards long, 5 yards high, and varied from
4 inches to 1 foot in width ; it consisted of nearly solid tinstone. In
the upper workings of the mine the more highly inclined portions of the
lode were found to be richer in tin than those portions in which the dip
was slight or moderate. At a depth of 70 feet, in the middle (or
deepest) shaft, the lode was split by a " horse " of granite, which
continues to the 300-feet level. The two portions into which the lode
is thus divided are known respectively as the foot-wall lode and the
hanging- wall lode. They vary in width from 6 inches to 4 or 5 feet,
and are usually banded in character. The " horse " is tin-bearing, but
is usually of low grade. The maximum width of the mineralised
formation, including the two lodes and the "horse," is 30 feet. In
places the horse has all the character of a stockwork, consisting of a
matrix of hornstone and quartz, intersected by minute veins of quartz
showing tinstone and arsenical pyrites. Occasionally the full width of
the formation has been extracted for a width of more than 25 feet, and
some remarkable timbering is to be seen, consisting of stull pieces,
havino: a length of as much as 27 feet 6 inches. The presence of con-
siderable quantities of arsenical salts in the mine-water appears to have
[new south wales, 87
a wonderful effect in preserving the timbers, and dry rot is apparently
unknown here. In the upper levels the lode was characterised by
clean and well-marked walls, showing slickensides, but in the lower
portions of the mine there are seldom any signs of defined walls, and
the country outside the hanging wall and foot wall lodes is as much
mineralised as the " horse " which separates them. Occasionally
tspecks of copper pyrites and small crystals of galena and zincblende
are seen in the lodes, bat these minerals never occur in any quantity.
The ore raised from the lower levels of the mine has for some con-
siderable time past yielded less than 3 per cent, of tinstone, so that it
is essentially a low grade as well as a refractory ore.
The lode has, for the most part, been worked by underhand stoping
the workings keeping pace with the excavation of the shafts. This is,
for many reasons, an unsatisfactory method of exploiting, but its adop-
tion is probably due to the continued low grade of the ore, and the
consequent disinclination of the owners to incur the expense of sinking
the shafts to a sufficient depth below the working faces to allow of the
subsequent removal of the ore by overhand or back stoping.
Other Lodes at the Ottery Mine, — There are several other parallel
lodes at the Ottery Mine which have, as yet, been scarcely prospected ;
one of these is situated about fifty feet to the east of the lode now
being worked, while another, which, judging l)y its strong outcrop,
would appear to be much the largest deposit in the district, is situated
about 200 feet still further to the east. There is every reason to
believe, therefore, that very extensive deposits of lode tin exist in the
neighbourhood, though the mining operations hitherto carried out show
that much of the ore is of lode grade. However, if ore containing less
than 3 per cent, of tin could be made to yield a margin of profit in
spite of the low price of the metal which has ruled for some years
past, the future should surely be hopeful in view of the largely
increased price now obtainable. In 1905 the Ottery Mine, Tent Hill,
raised and treated 2,500 tons of ore averaging 36 lbs, of Tin ore to the
ton. This returned 41 tons of ore valued at £3,250.*
The Jingellic Tin Lodes, — On the southern border of New South
Wales tin occurs in lodes at Jingellic, about sixty miles to the east
of Albury. Here again the mineral is found under the geological
conditions which mark its occurrence in the northern fields : that is to
say, the deposits occur in granite, close to its junction with slate rocks.
The lodes at Jingellic are situated principally in a high granite
range extending along the northern bank of the Murray River, at the
head of Swamp Creek. A flat about a mile in length extends from
the bank of the Murray up to the foot of the range, and here the
Swamp Creek forks, the western branch being known as Little Swamp
Creek. A company, known as the Jingellic Tin-mining Company,
formerly held about four hundred acres here, a considerable portion of
it being freehold land, and they also held the right to mine for stream-
tin on the flat ; much of their capital was, however, expended in
* Official Mines Keport, 1905.
88 TIN DEPOSITS OF THE WORLD.
unproductive work, and they suspended operations about eighteen years
ago, although very little actual prospecting of the lodes had been done.
*^ In tiie ranges above the flat no less than eight well-defined quartz
lodes occur, all carrying tin in greater or less quantity. No. 1 lode on
the range is situated at an elevation of about 900 feet above the river.
It strikes east and west, and is almost vertical, having a slight dip .
to the north. A tunnel was put in along the course of this lode for a
distance of 160 feet, and a winze was sunk for a depth of 30 feet.
The lode was found to vary in width from 10 inches to 2 feet, and the
quartz, in places, contains a large amount of tourmaline, with some
wolfram and a fair sprinkling of tinstone.
The most northerly lode is know as No. 6, and is situated about a
thousand feet north of No. 1, at an elevation of between 1,000 and
1,100 feet above the Murray, It also has an east and west strike, and,
so far as it has been tested, varies from 4 feet 6 inches to 6 feet in
width. Its outcrop has been traced for a distance of about a mile. It
appears to contain fine tin in streaks through the quartz, with only
traces of wolfram and tourmaline, while the casing carries coarse tin.
A shaft was sunk 70 feet on the lode (which measured 4 feet 6 inches
in width at that depth), and a tunnel was driven through the granite to
cut the lode at right angles. It was said that 10 tons of stone crushed
from this lode yielded 16 cwts. of tinstone. About 20 feet from this
lode, and running parallel with it, is a smaller one, varying from 4 inches
to 2 feet in width, and similar in character, carrying streaky tin in the
body of the stone, and coarse tin in the casing.
Between Nos. 1 and 6 four well-defined lodes occur, the outcrops
having been discovered to the westward of the two just mentioned, and
at a higher elevation on the range. The nearest to No. 6 is a
2 feet lode, bearing north-west and south-east, and therefore probably
junctioning with No. 6. No. 5 also probably junctions with No. 6 on
the south side. It bears north-east and south-west, and was opened at
an altitude of between 1,200 and 1,300 feet above the river. The small
excavation shows it to be 5 feet in width, inclusive of a " horse " of
granite 1 foot wide. The south side of this lode carries fair tin.
No. 4 lode bears E. 10^ N., and is 4 feet wide on the surface, and
6 feet 6 inches wide at a depth of 10 feet. It contains much arsenical
pyrites, some wolfram and tourmaline, and a fair percentage of tinstone.
Its outcrop has been traced for a distance of eight chains.
The next lode to the southwards. No. 3, is also a wide one, being
4 feet at its outcrop. It contains streaky tin, and appears to resemble
No. 6 in character.
Near the foot of the mountain, on Little Swamp Creek, is a lode
known as No. 7. It averages from 2 feet 6 inches to 4 feet in width,
and bears E, 38° S. A tunnel, which was driven from the foot of
the hill, intersefcts a shaft in the lode at a depth of 76 feet. A drive
was carried out to the east from this shaft, but the tin chute was
found to run out.
Another east and west lode occurs about a chain north of the last
mentioueJ ; it is about 2 feet 6 inches in width at its outcrop, and was
NEW SOUTH WALES. 89
formerly thought to be identical with No. 7. It contains coarse tin,
but appears to be patchy.
No, 8 lode, situated several chains still further south, varies from
10 to 18 inches in width, and strikes east and west. A shaft was sunk
on this for a depth of 70 feet.
The Dora Dora Deposits, — Tin also occurs in granite country at Dora
Dora, in the parish of Vautier, county of Golbourn, about 40 miles east
of Albury. A narrow swamp, through which Basin Creek flows, extends
back from the Murray River for several miles ; a stanniferous drift has
been proved to occur in the alhivials along the course of the creek.
The Pulletop Deposits, — Tinstone also occurs, both in lodes and
alluvial deposits, about twenty miles from Wagga Wagga, in the
parishes of Pulletop, Burrandana, and Westby, county of Mitchell.
Here again the lodes occur within a short distance of the junction of
granite with slate. The gangue of the lodes is quartz, and the tinstone,
which is accompanied by a considerable portion of wolfram, is only
present in small quantity. The largest lode has a width of about 3 feet.
Several attempts have been made to work the alluvial deposits derived
from the denudation of these lodes, but they have not so far proved re-
munerative, owing to the fact that tinstone and wolfram are present in
about equal proportions, and the product was unsaleable in Australia.
It is probable, however, that with the introduction of magnetic separa-
tors payable results could be obtained from the working of the drifts.
The Burra Burra Deposits, — At Burra Burra, about sixty-five
miles to the north-west of Parkes, an alluvial lead containing tinstone
was discovered in the year 1893, and was worked for a short time, but
the deposit was not found to be very rich or extensive, nor were the
lodes from which the mineral was derived ever discovered, probably
owing to the flat nature of the country. The depth of sinking in the
alluvium was as much as 20 feet.
The Euriowie Tin Lodes. — In the far western portion of the Colony,
at Euriowie and Poolamacca, about fifty miles to the north of Broken
Hill, tin-ore occurs under conditions which differ materially from those
of any of the deposits hitherto described. The Poolamacca and
Euriowie field was reported on by the late Mr. C. S. Wilkinson in
1887, and by Mr. J. B. Jaquet in 1894. The ore from this district
bears a most marked resemblance to that from the Harney Peak Mines
of Dakota, U.S.A., so much so that specimens from the two places
cannot be distinguished from one another.
At Euriowie the ore occurs in coarsely crystalline granite or
greisen dykes, which intrude metamorphic rocks, such as gneiss and
micaceous schist. The granite dykes are variable in their dimensions,
being usually from 1 to 20 feet, and occasionally 100 feet in width,
and terminating abruptly with rounded ends. Mr. Jaquet describes a
curious symmetrical arrangement of the dykes which is sometimes seen
at Euriowie. Ten or fifteen short dykes may be arranged in the same
general direction, and nearly, but not quite, continuous, the posterior
end of each being slightly to one side of, and overlapping, the anterior
end of its neighbour ; so that the series, when shown in plan, resembles
90
TIN DEPOSITS OF THE WORLD.
Pl\n of the Tin-beabino obanitio dykes oooueeino on the
Mount Euriowie Tin Mining Co.'s property.
ScaJet.
at>o
J^Teet
U/ter J.B.J^uet)
^Sh*ft 40 ft deeps,
\ I S N
Point 4 /s M2 feet from the south
boundary of M L A/9 44.
NEW SOUTH WALES. 91
a lode which has been intersected and heaved bj a number of parallel
cross courses. There are, however, no cross courses.
The dykes are composed of coirse crystals of quartz, felspar, and
mica, one or two of these minerals predominating at times ; thus the
rock may be mainly composed of large flakes of mica, or of coarse
crystals of quarts and felspar, or mica and quartz. The crystals of
tinstone, which vary in size up to 2 or 3 inclies in diameter, are not
evenly disseminated throughout the gangue, but occur in irregularly
distributed bunches.
The total product from the mines of New South Wales during 1905
was 804 long tons of metallic tin, valued at £188,377.
Tingha and Inverell Division. — There has been a considerable in-
crease in the tin output from this district, fully 1,800 persons are engaged.
The locality known as Red Hill has received a good deal of attention,
and a rich deposit of ore has been found at a depth of 100 feet.
At Pond's Creek great advancement is also noticeable.
Rich deposits have been opened up at Bora Creek, Barry.
Very little lode mining has been done, a quantity of stannite was
raised by the Conrad Mines at Howell during the year and stacked
for future treatment.
The dredges in this district have augmented the yield. A total
amount of 468 tons of tin ore were won, valued at £44,739.
From all other sources in this district 689 tons of ore valued at
£65,000 were recovered.
The total value of the tin won in 1905 in the Tingha and Inverell
Division was £110,239 as against £59,769 for 1904.
Promising lodes have been opened on the Inverell Road, a mile and
a half from Tingha, and at Red Hill and Stannifer, in the same
locality. In the JEmmaville Division 150 Chinese have been kept busy
sluicing tailings which had been cast aside in previous years. Con
siderable abandoned ground has been worked profitably, owing to the
increased price obtained for tin and to improved methods.
In the Deepwater Division an excess of water caused some suspen-
sion of work. The Silent Grove Mine, the most important in this
division, has yielded black tin averaging 8 hundredweights to the long
ton of ore raised. The workings there have been advanced about
100 feet. The Nine Mile Deep Lead has not been worked. The
expectations that work in the Broken Hill Division would be carried
on actively were not realised, and most of the leases have been can-
celled. Althouojh no great extent of new ground is being taken up, yet
the general indications are that the increased output will be maintained.*^'
Glen Innes Division, — The estimate for 1905 is £1,000 from ore
raised, this has been caused by a partial failure of the Glen Elgin
Dedging Company.
Rookahookra Division. — The miners working on the Mitchell
River are recovering considerable quantities of tin ore with the gold,
and an increased output is looked for from here.
* Official Keport of Secretary of Mines, N.S.W., 1905,
( 92 )
CHAPTER VIII.
TIN DEPOSITS OF QUEENSLAND.
Tin was first discovered in this colony at a place called Stanthorpe,
not far from the New South Wales border, in 1872, and has since then
proved an important item of production. Although not so widely dis-
tributed as silver or gold, tm has been found in many different parts
of the Colony, notably on the Pascoe River, near Weymoulh ; at
Bloomfield, near Cooktown on the Palmer River, the Barron Waters ;
Herberton, including Irvinebank and the Star River.
In 1896 tin was being mined for in six districts ; but two-thirds of
the output came from Herberton, and rather more than half from the
Cook district. In this year the production of tin was seriously de-
clining, but in 1903 and 1904 there was a big revival. The chief
Tin Mining fields are as follows : —
The Herberton Tin Field lies among the hilly country to the west
of the Herberton range, and is situated about 50 miles S.W. of the
Port of Cairns. The Mareeba to Chillago line has constructed three
branch lines to the tin-fields, which are very extensive, covering an
area of about 12,000 square miles. The whole country is very mouti-
tainous, ranging from 2,000 to 4,000 feet above the sea.
The tin mines are scattered in groups on both sides of the moun-
tains ; the rugged nature of the country has added greatly to the high
cost of haulage of ore and machinery, and the preliminary expense of
opening the mines.
Kangaroo Hill Tin Field, situated about 80 miles from Townsville,
to the N.W.
Stanthorpe Tin Field situated near the New South Wales border.
Tin has also been found near the Gilbert River in the west, near
the old Palmer Gold Fields to the north, and several other places.
* Herberton Tin Field. — The oldest rock formation of this
field is a series of alternating coarse and fine sedimentary beds.
They have been folded and faulted by high pressures acting
east and west, and are now generally found lying at high angles
of inclination, their irregular and broken lines of strike running in
northerly to north-westerly directions; these t-ocks have been altered by
long ages of pressure and chemical change, till the coarser beds have
* W. E. Cameron, Assistant Gov. Geo., 1904, "The Herberton Tin Field,"
published by Department of Mine', No. 192.
QUEENSLAND. . 93
been metamorphosed iuto quartzites aud greywackes, and the finer
beds into slates and schists«
Subsequently denudation has removed them over the greater
portion of the tin-bearing area, and has thus exposed the underlying
granite rocks over the greater part of the district.
The sedimentary rocks cover a very large district south of Irvine-
bank, and occur in small areas near Watsonville, Stannary Hills,
Koorboora, and California Creek. A great number of the more im-
portant lodes are associated with these rocks.
The plutonic rocks are Holocrystallinebiotiteor hornblende granite.
There are large areas of eurite types, such as granite porphyry and
quartz felsite. Lodes of tin occur in both. Dykes of elvan include
both the plutonic and altered sedimentary rocks. The tin lodes are
for the most part irregular in their manner of occurrence. The
deposits of ore seldom lie along a well-defined course between
the walls of country rock, but are as a rule distributed through
it in an irregular manner, forming bodies of very varied size and
shape. The lode material is only in exceptional cases separated
by well-marked planes of division from the enclosing country. As
a rule it merges into it, with a gradual change from lode material
to barren rock. The lode material is in almost all cases evidently
a product of the alteration of the country rock by the action of
mineralising agents, which have changed its constitution by chemical
action, and have at the same time deposited tin and other minerals
within its interstices.
In the case of the granite rocks the alteration to lode material takes
many forms, giving a variety of ores of widely differing appearances.
The alteration varies, however, more in degree than in general
character, and can, as a rule, be readily understood. The felspar and
other silicates may be changed to serpentine or chlorite, or may be
completely replaced by silica. In other cases the products of altera-
tion are sericite and silica. In some cases very little alteration is
noticeable to the eye, the tin occurring in grains through the apparently
unaltered granite or porphyry. The results are ores varying through
every degree of alteration, from the normal granite rock, splashed
through with grains of tin, to purely silicious tin-bearing material.
In the sedimentary rocks the lode material varies from an almost
unaltered quartzite, showing under the microscope crystals of tin in
the interstices between its grains, to a massive green chlorite, which
weathers on the surface to rusty-red kaolinic material. A normal
sample of " chlorite ore " from the 500-feet level in the Vulcan Mine
showed under the microscope a mass of grains of quartz and felted
patches of chlorite, splashed through with crystalline grains of tin and
magnetite. In the alteration of these greywacke and quartzite rocks
also the silicate minerals have evidently been first attacked, and
changed into chlorite by the mineralising solutions.
The fluoric minerals — topaz, fluorspar, and tourmaline — generally
found associated with tin deposits, are of very usual occurrence, both
in the lodes in the granite and those in the sedimentary rocks, while
94 TIN DEPOSITS OF THE WORLD.
the metallic minerals — wolfram, bismuthine, antimonite, galena, chalco-
prite, and magnetite — are frequent accompaniments, often in sufficient
quantities to be a source of considerable trouble in the treatment of
the ore.
Character of the Milling, — The irregular manner of occurrence
of the ore in these lodes has had a marked influence on the character of
the mining in this district. In the case of mineral matter introduced
Along true fissures, extending with comparative regularity over con-
siderable distances both horizontally and vertically, and carrying lode
material between well-defined walls, or impregnating the country rock
more or less evenly on either side, a certain amount of confidence can
be displayed in prospecting and development work. If the lode
becomes too narrow or too poor for profitable working, development
work is pushed on either horizontally or in depth along the line of
fissure, with a fair prospect of the lode again widening or improving
in value along the same line. Where, however, no such irregularity of
disposition of the ore exists, as in the case of most of the Herberton
lodes, only the general run of the ore body can be followed as a guide
for fresh prospecting work.
One of the most noticeable features of the ore bodies is the short-
ness of the shoots in horizontal extent. In the Launcelot Mine at
Newelton, at the 150-feet level the lode has been s toped for 200 feet
continuously on ore. The next longest working on a continuous body
is at the 500-feet in the Vulcan Mine, where the stope has been carried
along for about 150 feet on ore. At the 100-feet level in the Smith's
Creek Mine the ore was taken out for about 78 feet in length. These^
however, are three of the longest continuous shoots that have been
worked on the field, the majority rarely reaching 50 feet in lengths
Nor do they often lead on to others in the same line connected
genetically with them, and capable of being worked from the same shaft.
Their want of length is often compensated for, to some extent, by
considerable thickness, and bodies of ore of nearly the same dimensions
in either direction are of frequent occurrence.
The greatest hindrance to continuous and economic mining of these
lodes is, however, the want of continuity of the shoots of ore as they
are followed downwards. Repeated instances of unsuccessful attempts
to pick up large and profitable shoots of ore by driving 50 feet or
100 feet below where they are being stoped have convinced the tin-
miner in this district that his hopes of picking up a lost lode again in
the position in which it might naturally be expected are more often
disappointed than not. Frequently a long period of prospecting in
different directions has to be gone through before fresh ore reserves can
be developed, with often little or no indication except the general dip
of the shoot above to serve as a guide.
The want of continuity of the deposits makes the economic
location and proving of fresh ore reserves, in advance of those already
developed and in course of extraction, a matter of the greatest impor-
tance. Where the lodes follow no true course, as such is understood
with true fissure lodes, and where the break in the continuity is not
QUEENSLAND. 95
due to the faultiDg of the country subsequent to the formation of the
ore body, it is useless to attempt to apply rules of procedure for finding
lost lodes that have been framed to suit well-defined deposits with
definite course and dip. The only course open seems to be that uni-
versally adopted by the experienced tin-miner — namely, to follow the
tin as far as it will lead, in the hopes of its making into another body
of ore, and when this can no longer be done, to use the individual
judgment in prospecting in the most likely place in the most economic
manner that can be employed. In this connection it seems likely that,
in the case of large bodies of ore like those found in the Vulcan,
Smith's Creek, and many other mines where the tin is disseminated
with comparative evenness through an extensive mass of lode material,
the diamond drill might be employed with advantage by saving much
profitless driving and sinking, and allowing of the opening up of fresh
ground in the most convenient manner. In any case the importance of
keeping development work well ahead of present mill requirements
cannot be too strongly insisted on with lodes of this character, if the
undertaking is to prove profitable to the shareholders.
The small size of the great majority of the lodes, combined with
their richness, has made them peculiarly adapted to return good profits
to small parties of working miners. Their bunchiness and want of
regular continuity when followed downward frequently gave rise to
correspondingly irregular methods of working, often entailing two or
three handlings of the ore before it could be brought to the surface. In
this way the depths were soon reached at which it became impossible
to handle anything but the richest ores at a profit, and the majority of
the lodes were gradually abandoned before any great depths had been
reached. Many of the larger ore bodies, especially amongst those
occurring: in the sedimentary rocks, were early found to be too poor
for profitable mining with the low price ruling for tin before 1898.
They were abandoned at shallow depths. Increased prices, however^
inspired the hope that many of these could be made to yield profits if
provided with batteries close at hand, and with the application of more
up-to-date methods of mining.
* Last year's yield of tin amounted to 3,945 tons, of a value of
£297,454, being an increase in quantity of 22 tons, and in value of
£27,178.
More than two-thirds of the supply in 1905 has been derived from
that portion of the Walsh and Tinaroo Mineral Fields which may be
roughly described as extending from the town of Herberton, in a
southerly direction, to the confluence of Return Creek with the Herbert
River ; thence westerly about 15 miles ; thence north-west to Koorboora ;
thence east-north-east to Stannary Hills ; and thence east-south-east
to the point of commencement. Within this area of approximately
1,000 square miles tin is the principal paying product ; and, although
it is probable that many valuable lodes have yet to be discovered, there
are certain centres around which the productive mines are grouped, and
* Annual Beport Secretary of Mines, Queensland, 1905.
96 TIN DEPOSITS OF THE WORLD.
which at present supply practically the whole of the lode tin of the
district. Chief of these is Irvinebank, and there is the Vulcan, the
deepest and the richest tin mine in Queensland. The straight shaft is
now 1,100 feet deep, and at 1,050 feet a level is being driven for the
lode. The lowest working level in tin ore is 900 feet, and from this
point up to 675 feet there are large reserves almost untouched. Most
of the year's output came from the 600-feet level, but stone is still
being raised from the shallower parts of the mine, where it is quite
possible that further exploration may disclose new bodies of ore. Next
in rank to the Vulcan is probably the Governor Norman, a compara-
tively new discovery, which has, however, been opened sufficiently to
furnish the assurance of the existence of a very large deposit of ore-
bearing material carrying a little over 3 per cent, of tin. Although not
80 rich as the Vulcan, its great dimensions will, it is believed, when
development work is more advanced, aud when more crushing power
is available, render it a formidable rival of that mine. There are in the
neighbourhood of Irvinebank a number of other mines in various stages
of development, all dependent for the treatment of their stone on the
London mill ; and, in order to relieve the pressure, it has been decided
to reopen the mill at Coolgarra, which it is hoped will stimulate into
activity that latterly somewhat neglected centre.
Next in productiveness to Irvinebank come Stannary Hills, where
the Stannary Hills Mines and Tramway Company has, under the
direction of a new manager, been entirely reorganised.
It must not be forgotten that the question of rainfall plays an im-
portant part in deciding upon the possibility or otherwise of working
alluvial deposit to advantage, hence the very marked increase in the
production of stream tin in the Herberton district during the last two
years, due to a rainfall much in excess of that which has fallen for a
number of years. For instance, the value of alluvial tin won during
1903 was £45,287, as against £7,835 for the previous year.
Stanthorpe. — Although immense quantities of tin have been taken
from the creeks and flats of the Stanthorpe field, and. the days of
washing and cradling are over, there is still left much that may be
recovered by modern appliances for the economical treatment of large
quantities of material. With this object in view, two (iredging com-
panies have acquired considerable areas of tin-bearing country,
and after numberless difficulties and delays are now in active operation.
Stanthorpe Proprietary Tin Dredging. — The annual report
of the director of the Stanthorpe Proprietary Tin Dredging Company
shows that during the past year the dredge recovered 93 tons 14 cwts.
5 lbs. of tin, for which the sum of £10,019 10s. was received. The
expenditure totalled £6,069 4s. 6d., of which sum £2.303 15s. lid.
went in wages ; renewals, repairs, &c., £1,522 ; sundries, freight, car-
riages, £539 lOs. Id. ; firewood, £473.
The Kangaroo Hills Mineral Field.
Geology. — The Kangaroo Hills Field covers an area occupied hy
altered sedimentary rocks and granite. The former occur in a belt ex-
QUEENSLAND. 97
tending along the lower valleys of the Running River and Oaky Creek
as far as their junctions with the Burdekin. They are surrounded by
granite on all sides, except on the west, where a newer series of sedi-
meatary rocks overlies both them and the granite on the western side
of the Burdekin River.
* " The country rock of the whole of the mining district (as exploited)
consists of alternatioQS of mica schists, talc-schists, grey wacke, grits,
conglomerates, quartzite, and limestones. The schists and quartz ites
are frequently interspersed with minute garnets, which are at times so
numerous that for practical purposes I have designated them * garnet
rock.' The whole of these rocks are highly inclined, frequently
vertically, and so much broken up by faults, that it is impossible to
trace any individual bed for more than a few chains. Beds of lime-
stones are met with along the south-west and north-east belt of
mineralised country already referred to in a previous paragraph, as well
as among the Mount Brown group of mines. These limestones have been
traced for many miles ; the outcrops of the limestone show that they, as
well as the * adjacent sedimentary rocks ' have been tilted up, contorted,
and literally chopped up into pieces by faults, but also that the limestones
themselves were originally isolated deposits, probably coral reefs.
" The limestone beds vary considerably in character, but all have
suffered a great amount of alteration. The prevailing type is a white
crystalline or saccharine marble. It is generally free of silica, but, on
the other hand, some beds, having originally been charged with siliceous
sand, now present little more than a skeleton of silica, the calcareous
portions having yielded more to denudation. Sometimes, in the com-
paratively pure limestone or marble, the segregation of siliceous matter
has formed a network of veins. In a limestone so highly metamorphosed
it is not surprising that distinguishable organic remains are souorht for in
vai n . I have indeed seen a few fossils which could be recognised as corals,
although but slight traces of their outlines or structure were preserved.
" The age of the stratified rocks must for the present remain an
unsettled question, Mr. Maitland doubtfully refers them to the
' Burdekin Bed ' (Middle Devonian), believing them to be continuous
with them, as they are developed lower down the Burdekin Valley,
where they afford an abundance of characteristic fossils, as well as to
be similar in lithological character. But it must be confessed that there
is little evidence either for or against this view.
" The stratified rocks are pierced by masses, of limited extent, of
intrusive acidic * felstone,' or felspar and quartz -porphyry, a rock com-
posed of orthoclase felspar with blebs of quartz."
Wherever the boundary between the granite and sedimentary rocks
is well exposed, the intrusive nature of the granite, and consequently
its later age, is made clear. A good example of this is seen on
the left bank of the Running River, on the track between Ewan and
the Macaulay Creek Mines. At this point a gully coming out from the
granite hills exposes the upturned quartz ites of the sedimentary beds in
* R L. J., Brisbane, "The Kangaroo Hills Silver and Tin Mines," by authority,
1892.
VS TIN DEPOSITS OF THE WORLD.
contact with the granite, with tongues of the latter passing into then).
The sedimentary beds are thus seen to be older than the granite, but
further than this no evidence was forthcoming as to their stratigraphical
position. The granite is perfectly normal in character, being composed
for the most part of pink or white orthoclase with quartz and biotite
mica. Intrusive dykes of diorite and also of eurite were observed at
Macaulay Creek and Hidden Valley.
Tin Mining. — All the tin lodes at present being worked occur in
granite country. The two main centres of prospecting are : — Firstly,
the lodes in the neighbourhood of the proposed township of Kallanda,
about 12 miles up Oaky Creek from the Burdekin River ; and secondly,
the lodes in the ranges at the sources of tlie Running River. The
former comprise the properties of the Waverley, Planet, Kangaroo Hills,
and Douglas Tin Mining Company, with various minor shows. The
latter are still held by parties of working miners, having not yet reached
the company stage. On one lode only has machinery as yet been em-
ployed, none of the workings being over 100 feet in depth.
* The year's record at Kangaroo Hills cannot be said to have been
in any way eventful. The Waverley Company continue their policy
of sub-leasing their mines and of opening their mill for the treatment
of public stone on liberal terms.
For the last twenty years the mountainous country surrounding the
head waters of the Annan River, some 30 miles south from Cooktown,
has been the resort of the tin miner, and large quantities of tin have
been won. The operations of the individual miner have, however,
necessarily been confined to those creeks and gullies where water could
be obtained, and attempts to develop the field on a more extensive
scale have hitherto proved abortive. A powerful company, registered
in Melbourne and in Queensland as the Annan River Tin Mines, No
Liability, have now acquired some 400 acres of alluvial and lode ground
in the neighbourhood of Mount Leswell. The success of the venture is
largely dependent on the ability to secure an efficient water supply, and
since November last the company have been actively engaged in con-
structing a race from Finlayson Creek to the mines, a distance of 7 miles,
by which they hope to conduct water sufficient for sluicing purposes,
and also for driving the battery that they mean to erect.
t Alluvial tin assaying 72 per cent., has been discovered on the
Robertson River, about 40 miles south of Georgetown.
At the Majestic Claim, in the Townsville district, a tin lode has
been found, 20 feet in width, assay £4 per ton, and another expected
to bulk £3 per ton. There are also a couple of smaller lodes.
I The New Era, Northern Queensland, one of the lowest grade
payable tin mines in the Commonwealth, the crushing stuff averaging
only '64 per cent, black tin, or about "45 per cent, white metal. Yet
a profit of £1,100 has been made out of 4,800 tons. The mine is
owned mostly by the men at work in it.
* Gov. Annual Report, 1905.
t "Mining Journal," Nov. 3, 1906.
X " Mining Journal," Oct. 27, 1906.
TASMANIA.
I TIN OePOsiTft
« C
MAP OF TASMANIA— SHOWING POSITION OP TIN DEPOSITS.
( 99 )
CHAPTER IX.
TIN DEPOSITS OF TASMANIA.
The tiQ deposits of Tasmania are situated in the north-eastern and
north-western side of the island, with some comparatively unimportant
deposits on the west and east coasts. The deposits of the most econo-
mical value are situated in the north-eastern portion of the island.
Mr. W. H. Twelvetrees, the present Government Geologist, writes the
following description of the Anchor Tin Mine and Blue Tier district :
" The granite of which the Tier is composed is that which, with
textural and slight mineralogical variations, is the basement rock of the
whole of the east coast of Tasmania. At the close of the Silurian
period it consolidated upon intrusion, at great depths, into the Silurian
slates and sandstones. The extent to which the latter have been meta-
morphosed and mineralised by the invading granite can be well studied
along the zone of contact, near St. Helen's.
At the Tier it is a rather coarse-grained porphyritic granite, with
large crystals of felspar, an inch in length, scattered through it ; grey,
white, or pink in colour. Its mineral constituents are felspar, quartz,
dark magnesian mica (biotite), and a little silvery potash mica (musco-
vite). Sometimes the white mica is quite absent ; its abundance seems
to depend upon the presence of tin-ore. At George's Bay the granite
contains a larger proportion of quartz and less felspar than upon the
Tier. The first element to crystallise was the mica, then the felspar,
finally the quartz. This is shown by crystals of mica occurring enclosed
in the felspars, and by the residual silica filling the interstices or spaces
between the well-formed crystals of felspar. So far, all are agreed.
The differences of opinion begin when we consider the portion of the
granite which carries the tin-ore. This is not s(^ coarse as the ordinary
granite ; it is more even-grained, and is not porphyritic. The dark mica
goes through a series of changes into silvery and greenish-white mica,
muscovite (non-pleochroic). The change is first into a dark bronzy
mica, and finally, as the iron becomes gradually abstracted, into the
white potash variety. This alteration can be observed under the
microscope in one and the same crystal, which is partly iron-magnesia
and partly potash. Often the felspar decays to kaolin, and the rock
becomes softer, or there is extreme silicification, and the rock grows much
harder. The magnesia liberated in the decomposition of the dark mica
is re-deposited as talc, which gives a greenish tinge to much of the tin
G 2
100 TIN DEPOSITS OF THE WOBLD.
granite ; the felspathic material remains behind, to some extent, as
kaolin. The new minerals developed in this variety of granite are
cassiterite, wolframite, scheelite, fluorite, molybdenite, galena, copper
pyrites. The iron pyrites may be original. No axinite has been yet
found at the granite contact ; this is no doubt owing to the absence of
lime. Tourmaline is rare. Sapphires and topaz are fouhd in the
stanniferous gravels, and have probably been released from pegmatitic
veins.
This tin- bearing granite has been labelled with different names, such
as quartzose porphyrite, aplite, and, most frequently of all, quartz
porphyry. Parts of the mass correspond with some of the tin -bearing
granite at Altenburgh, in Saxony, called zwitter-rock, or stockwerk
porphyry, only the latter usually has a good deal of topaz in it. Zwitter-
rock is sometimes a greisen (quartz + mica), with very finely dissemi-
nated tin-ore ; sometimes the mica is absent. The mica itself is a
greenish fluoric potash-iron variety, which, together with topaz, has
replaced the felspar. At other times the rock is nearly all quartz, and
dark in colour, resembling the more quartzose varieties of the Blue
Tier tin-granite. Typical zwitter-rock contains — quartz 50 per cent.,
mica 37 per cent., topaz 12 per cent., cassiterite 0'4 to 0*5 per cent.
Varieties without mica consist of 70 per cent, to 71 per cent, quartz,
27 to 28 per cent, topaz, and I'd to 1*5 per cent, cassiterite. Zwitteris
essentially a modified granite, resulting from a process of greisenisation
which has started from cracks and fissures.
The most dyke-like occurrence which I saw was on Haley's Lease,
on the old Blue Tier Company's ground, not far from Mr. Ogilvie'&
camp. In the race a dyke-like band of tinstone is exposed for a width
of two chains, running through the porphyritic country granite, from
which it is separated by a small pegmatitic vein. Further east a smaller
band of soft tinstone, 1 foot wide, traverses the granite, and has quite
sharply defined boundaries. Still further east, a wider vein of tinstone
is seen, also separated from granite by a pegmatitic facing. I have
alluded to this stanniferous variety of granite as tinstone, but am not
sure that it is the best term, as it is also used elsewhere for cassiterite,
the ore of tin. The above occurrences cannot be considered as conclu-
sive, for they are associated with pegmatic veins, which may have been
the mineralising channels.
The two strongest objections to the dyke theory are : —
1. The irregular boundaries of the tin-bearing granite ;
2. Its occurrence in the form of floors.
At the Anchor mine it disappears to the north and east under a
capping of country dark mica granite, a very singular thing if it is a
dyke. To the north-west and west the Anchor stone extends to the Crystal
Creek, passing under some country granite on the east side of the road
bridge ; then, west of the creek, the altered granite, at first non-stanni-
ferous, and then tin-bearing, continues west through the tin properties of
the Crystal Hill and Liberator Companies, merging into ordinary country
granite at the Working Miners' Creek, on the western boundary of the
Liberator. Again, from the Crystal Hill, a narrow strip of tin granite
TASMANIA.
101
extends at right angles to its previous direction, due north through the
Australian sections and Haley's Lease, across the Wyniford to Beales'
sections at Mount Michael, spreading out like a fan as it approaches the
Wyniford, and, apparently, connecting with the Moon property on the
east. In the middle of the Crystal Hill sections, some of the unaltered
country granite has survived. The irregularity of the contour of the
formation seems irreconcilable with a dyke origin, and, in addition, the
general structure of the stone differs from that of elvan dykes. The
latter are generally coarsest in the middle, and finer grained near the sides.
Apart from elvans, wide granite dykes often traverse granite masses,
but in the present case there is no parallelism of the sides of the formation
— no walls, nor anything to suggest that the tinstone is the filling of a
fissure.
There is a very striking indication of floors in the Anchor Mine.
The tinstone in the old eastern workings lies under the barren country
granite, which ascends the hiu thence to Lottah (see Fig. 22) ; a flat
FIG. 22.-0'. Granite. T.G. Tin granite.
seam of quartz and bronzy mica, with a few large felspars, forms a
horizontal floor separating the tin-bearing stone below from the coarse
(here decomposed) granite above. A face of about 30 feet of the latter
is exposed at this bench. Just below the seam is some white quartz
and coarse tin, and, within 6 inches of it, I noticed a large felspar crystal
quite enclosed in the tinstone ; this was evidently due to the influence
of the dividing seam. We have here a good example of a horizontal
boundary or floor. Practically the same phenomenon is repeated in the
top workings of the mine, where dark mica granite rests upon the tin-
stone, and has to be stripped before the latter can be worked. This
102 TIN DEPOSITS OF THE WORLD.
granite overburden may be expected to decrease towards the west, and
increase towards the east. I infer this from the fact that the modified
stone rises about 400 feet to the road in a north-westerly direction,
while northwards it is hidden beneath the huge granite mass which
ascends from Lottah to Poimena. On Haley's Lease, at the old
McGough's tunnel-pit, 1,400 feet above the Anchor face, the country
granite (also decomposed) occurs overlying the tin-rock, as shown in
Fig. 23.
TG
FIG. 23.— C Granite. TG. Tin granite.
Dykes, — There are a few dykes of eruptive rock, which traverse the
granite. These are basic, and have usually been taken for Tertiary
basalt, which they greatly resemble. Microscopical examination shows
them to be dykes of diabase. [Constituents = plagioclase felspar +
augite, the latter being greatly chloritised : structure = diabasic. No
olivine.] There is a dyke of this kind, about 50 feet wide, in the
granite, crossing the road S. of Lottah at the Horseshoe bend, between
Lottah and the Anchor manager's house, and said to be traceable east-
wards for 3 or 4 miles. Stones belonging to the same dyke are seen on
the track near the office at the Anchor Mine.
I saw a wide dyke of similar stone on Haley's Lease, a little north
of Ogilvie's camp. There is another one on the Lease about 30 chains
further north. These dykes are all roughly parallel, taking a N.E.-S. W.
direction. They are of Mesozoic age, consequently younger than the
deposits of tin-ore, and have no bearing whatever upon its deposition.
Distribution and Grade of Ore. — The quality of the tin-ore from
the Blue Tier mines is excellent. The average of the whole district is
about 72 per cent., some of the produce reaching a higher figure. The
ore is remarkably free from iron ; in some of it, however, traces of
copper are present.
There seems to be no rule for making use of the distribution of the
ore in the tin-granite (^Germ. Zinngranit). I could see nothing to show
whether the tin has been concentrated in the middle of the formation
more than towards the margins, or vice versa. The patches are quite
TASMANIA. 108
irregular, and will, I believe, be found to be more dependent upon the
natural fissuring of the rock than upou any law of segregation. In
some places the stone is rich and heavy ; elsewhere, practically barren.
Taking the formation as a whole, the probabilities are that the ore
contents will range from a shade under f to about f per cent,
black tin. An average of J per cent, ought to be expected from most
of the mines.
The percentages ruling at the different mines are : — At the Anchor,
about f per cent., passing all stone through the mill ; Australian, | to
nearly 1 per cent. ; Liberator ranges from i to nearly 1 per cent.,
averages f to | per cent. ; Haley's Lease used to yield f per cent. ; the
Moon, J to 1 J per cent. At the new Crystal Hill Mine, now being
opened out, I took samples from each face indiscriminately, without
picking or seeing whether any tin was visible or not, and the total assay
was 0*6 per cent, metallic tin, or (at 70 per cent.) 0*85 tin-ore. Large
deposits of f per cent, stone undoubtedly exist, but then, again, poorer
areas come in to reduce the average, which from all appearances is ii>
the neighbourhood of ^ per cent., taking the Tier as a whole.
The Anchor stone appears to be the lowest on the list, and in the
district it is generally considered the poorest stuff. I fancy this is
largely owing to the fact that the mine is being operated upon a large
scale, and that the stone is not selected, but broken down from the faces
and passed through the battery just as it comes. It is certain that if
the other mines commenced to clear away the whole of their formation
without selecting promising places at which to attack the deposit, the
per cent, yield would be somewhat reduced.
Anchor Mine.
This is the most important and best equipped mine in the district*
It is situated just to the S.W. of Lottab, on the slope of the hill above
the Groom River. It was reported upon by Mr. Thureau in 1886, and
again by Mr. Montgomery in 1889 and 1893. Work has been carried
on here for over 20 years intermittently, but until the present management
took the mine in hand imperfect and costly methods had been the rule.
Prior to the end of 1892, 30,734 tons were crushed, returning 288 tons
tin-ore, equal to 0*937 per cent., but with work on a larger scale the
average yield of the stone has decreased. For the 2 1 months ending June
1901, 111,167 tons stone have been crushed for 434 tons tin-ore, equal to
0*39 per cent. The company 'i ground covers 315 acres, but the actual
work of winning ore is, so far, confined to an area of about 12 chains
square, which is being slowly enlarged as the upper face advances north
into the hill. The formation, or matrix, of the ore is the tin-granite
described above. Generally, the felspar of the granite has not been
wholly removed, and the rock is not very hard. In the Pentridge face^
however, the rock is quartzose and excessively hard ; so hard that it
has been taken for lode-stuff. It belongs, however, to the same forma-
tion as the other. This eastern face carries good stone, of a quality
near 1 per cent. Twelve feet below it 100 tons of tin-stone were taken
i04 TIN DEPOSITS OP THE WORLD.
out by Mr. Mitchell, yieldiog 2 per cent, tin-ore. A tunnel has been
driven 150 feet into this hard rock, and 75 tons of stone, taken out for a
trial, gave 1 per cent, tin-ore.
JThe faces now being worked are 10 or 12 chains west of the above
workings, and extend up the hill for a vertical distance of about 200 feet.
No. 1, the lower face, forms a crescent 300 feet in length by 55 feet in
height. The whole of the rock is broken down and trucked to the
stone-breaker without selection, for all of it contains tin. Green mica
and talc give a greenish tinge to the rock. A little fluorspar accom-
panies quartz leaders ; no bismuth or galena has been observed, only a
little copper pyrites. Special concentrations of ore may be seen in floors
of the greisenised rock and in nests. The principal joints and seams
run E.W, and N.S. ; minor ones traverse the rock in all directions. Tin
is always looked for in and near the seams.
No. 2 face is about 150 feet above No. 1, and No. 3 is 50 feet above
No. 2. I ought to say that 35 feet below No. 1 a tunnel has been
driven for 250 feet, and 50 tons of stone were taken out and raised by
horse-power to the stone-breaks, and returned a good yield at the
battery. It may be added that in the No. 1 face the stone on the whole
keeps the same in quality from top to bottom, with, of course, richer and
poorer patches occasionally.
No, 3, the uppermost face, has more stripping than the others, and
the tin formation is covered by about 18 feet of country-granite, of
which there is only a little in the N.W. corner of No. 2 face, and
none at all lower down in No. 1 face. The tinstone in the upper
face is of the usual character, except that it carries more leaders of
stanniferous quartz.
A new epoch in the history of the mine commenced when the present
general manager, Mr. R. Mitchell, took charge of the work, and re-
adjusted the dressing plant. New faces were opened, and the property
was prospected, both by tunnels and boring, with the diamond-drill. In
1899 nine bores were put down, five of which are in advance of No. 1
face, three being near the old eastern workings, and No. 9 600 feet
further north. As a general result the bores show that the rock is
variable as a tin -carrier.
The dressing sheds contain two ^50-head batteries, with 1,000 lbs.
stamps and accompanying classifiers, jigs, vanners, settlers, and buddies ;
the dressing is automatic and efficient. With full water supply, the
lOO-stamps will crush 100,000 tons of stone a year ; but, unfortunately,
for want of water, the 100-head have never run for long continuously,
and the average number running last year was only 34. The manage-
ment claims that when in full work the ore can be raised and treated for
2s. 6d. per ton of stone. The average hands on the pay-list for the past
twelve months have been 112, and for full work not more than about
30 additional would be required. It is easy to see how desirable it is to
obtain water-power sufficient for driving the complete plant.
The company have water-rights for 48 head, and if that amount of
water could be obtained, there would be no difficulty in driving the
whole of the crushing and dressing plant. The new race, when com-
TASMANIA. lOo
pleted, will exteod 39 miles to the South George River ; the first
section goes 26 miles to the North George, tapping Waratah Creek, etc.
on the way, and the remaining 13 miles to the South George will be
constructed subsequently.
Assuming the grade of ore to continue, and it seems safe to do this,
the quantities necessary for success may be reasonably considered as
existing. The ground for some depth below the lowest face and between
the lowest and the top faces has been proved by the diamond-drill to be
tin-bearing. Of course, in this area there are poOr patches as well as
good ones, but there is no doubt of the tin-bearing formation existing con-
tinuously north and south between the faces for a total horizontal
distance of 8 chains, and I think it may be legitimately accepted that
the per cent, value of the stone for that distance will not be less than
that shown by the battery returns the last few years, viz., 0*39 per cent.
The width of the formation has been proved for about 12 chains, but
there is a good deal of broken ground, and, in my calculation of quanti-
ties which may be reckoned upon, I have confined myself to the width
of the present workings, viz., 4 chains, leaving on one side the eastern
ground, the value of which cannot be easily estimated. The eastern
ground will probably swell the total output. The proved block of stone
to be taken out will then measure 8 chains long by 4 chains wide by
to 200 feet high, which (with a sp. gr. 2-67 X 62-425 = 166*67 lbs.
per cubic foot) will total 1,037,142 tons, or, allowing 20 per cent, for
barren interspaces, 829,714 tons tin-bearing stone. This quantity will
suffice to feed 100-head of stamps continuously for eight years, and the
tin-ore contents at 0*309 per cent, would be 2,563 tons. This output
can be increased by the produce of the eastern workings, but most of
all by the advance of the faces into the hill north of the present upper
workings. The eastern workings cannot be extended far to the east
without coming under a heavy cap of country-granite ; still, the ground
explored up to date there will give a large output. Again, in the
principal workings every additional chain of width taken in the face
means nearly 200,000 tons more of material, or a couple of years' more
work between the levels of existing faces.
A question of interest is whether the tin-granite will rise with the
hill, or the overburden of barren granite increase as the work advances.
From my examination of the country surrounding the workings, I am
led to believe that the overburden will be heavier east and north of the
present works, but that it will decrease towards the west and north-
west. Tin-granite is seen on the road north-west of the mine and
500 feet above the lowest face, and I believe the future development of
the mine will disclose a continuous vertical section of 500 feet ; but
whether it will all be payable stone cannot be ascertained beforehand,
except partially by use of the diamond-drill. The tunnel below the
lowest face has also shown that very good tin-bearing stone is going
underfoot. The full quantity of stanniferous rock existing on the pro-
perty cannot be estimated without making assumptions unverifiable in
the present stage of development. It is not known, for instance, how
far the percentage of tin may fall in the zones of rock which have not
106 TIN DEPOSITS OF THE WOBLD.
yet been proved ; and, without further boring, it is not absolutely certain
that concealed floors of barren granite may not interrupt the continuity
of the formation here and there. But if, after extending the present
faces right across the property, the ground throughout proves good
enough to send to the battery, then I estimate there is stone enough on
the company's sections to keep the mill going continuously for between
40 and 60 years.
Anchor Tin Mines.
Stamp
Tons
Yield
Cost
working.
crushed.
Black Tin.
Tons. Cwt.
per ton.
s. d.
June 30, 1899
46
38-179
131
3 10
„ 1900
38
40-838
152
15
5 5
„ 1901
33
38-190
140
16
5 11
„ 1902
43
41-530
146
5
5 2
May 13, 1904
76
108-529
258
3
3 5
June 30, 1904
91
136-655
243
13
2 10
„ 1905
74
118-634
190
7
2 5
The Tin deposits of the Ben Lomond District were at one
time extensively worked. The following account of the geology of
this district is taken from the Government Geological Survey of
1901 :—
"Ben Lomond is situated about 14 miles north-west of Avoca, and
the mining district lies to the south of the mountain. The general geology
of the district is, with the exception of some of the occurrences of the
greenstone and Mesozoic strata (which do not affect the mining industry
in this district) very simple.
" The bedrock of the district is granite of Devonian age. This
rock solidified under a probably massive covering of Silurian sedi-
mentary rocks — slates, sandstones, etc. — but these have long ago been
removed over the greater part of the district. Remnants, however,
remain in several places, especially in the eastern and north-eastern
parts of the field, where, in the vicinity of Storey's Creek, a consider-
able area is still covered by Silurian strata. These rocks are also found
in the north-western portion of the field, and further south very small
isolated patches are sometimes encountered on the summits of the
highest ridges. The denudation and removal of the Silurian strata
must have taken place during the later portion of the Devonian period,
for, lying on the top of the granite, and often covering the remnants
of Silurian strata, we find horizontal beds belonging to the Permo-
carboniferous period. These have, however, also been very largely
denuded, and in the southern portion of the field are for the most part
confined to the tops of the granite spurs, where the harder grits and
sandstones have resisted denudation and have protected the softer or
more easily decomposed granite underneath. Much of the northern
portion of the field is overlaid by quite a thin layer of Permo-carbon-
iferous strata, and through this the granite outcrops frequently.
Further north, on the slopes of the mountain itself, the carboniferous
strata increase in thickness until the perjiendicular cliffs of columnar
TASMANIA. 107
greenstone which form the massive capping of the mountain are
reached. The contact, however, of the columnar greenstone and the
Permo-carboniferous rocks is obscured by a heavy talus of greenstone
blocks fallen from the mountain. Next to the Permo-carboniferous
strata in question of age are the Mesozoic strata, which are mentioned
by Mr. Montgomery * as occurring on the mountain at an elevation of
4,000 feet above sea-level, and overlying the greenstone. I found
typical felspathic sandstone of Mesozoic age in the valley of Gipp's
Creek, at an elevation of only 1,400 feet, apparently underlying the
greenstone. These rocks are exposed in steep cliffs, rising up on the
western side of the creek for a height of about 200 feet. Above these
there are, perhaps, 500 feet of columnar greenstone. The dip of sand-
stone is about 15° or 20® to the south-west. On the eastern side of the
creek we find horizontal Permo-carboniferous sandstones resting on the
granite.
"The eruption of greenstone took place towards the end of the
Mesozoic period, as has been proved in other parts of the State. Its
relation to the Permo-carboniferous and Mesozoic strata are extremely
various and perplexing, sometimes overlying, sometimes underlying^
and sometimes breaking through these rocks.
" The majority of the granites in which the deposits of tin ore occur
are composed essentially of felspar and quartz, there being very little
mica present. Much of the felspar (prthoclase) occurs in fine large
crystals of the Carlsbad twin type, distributed porphyritically through
the ground-mass of the granite, which is composed of a finer-grained
but thoroughly granular mixture of quartz and felspar. In many
places a rock very much finer grained than the granite, but composed
of the same constituents, is to be seen. Only once did I observe this
rock in situ, and then it formed a small dyke in the granite. It is
probable that the other occurrences are of the same nature. Quartz
porphyry also occurs, sometimes forming the margin of the granite
mass, but at other times possibly forming dykes in the granite. One
interesting occurrence is to be seen on the old Republic Mine, where a
quartz porphyry occurs with perfect double-ended crystals of quartz
distributed through it. The granite is traversed by numerous veins of
pegmatite, varying very largely in composition ; occasionally they are
found composed mainly of giant crystals of quartz, felspar, and mica,
with needles of tourmaline, and in one conspicuous instance with very
large crystals (up to 2 J inches in diameter, and 5 or 6 or even 10 inches
in length) of beryl embedded in the quartz. Mr. W. H. Twelvetrees
has examined thin sections of this beryl under the microscope, and has
proved the presence of minute enclosures of liquid carbonic acid, prov-
ing that the mineral has been deposited under conditions of very high
pressure. The pegmatite veins very frequently contain tin ore, and in
one case — the old Lomond Mine — extremely rich patches of tin ore
were found in a small vein of pegmatite. A very small proportion of
the tin is found in the veins themselves ; it is found very much more
Keport on the Ben LomoQcl District, May 5, 1892.
108 TIN DEPOSITS OF THE WORLD.
abundantly in the rock on either side of the veins, and very often the
vein is so small and so insignificant, in comparison with the impregna-
tion which has taken place from it, that it may very easily escape
notice altogether. The typical tinstone of ^he district occurs as a hard,
highly quartzose granular rock, seldom containing true mica, but
frequently a massive mineral of almost the same composition, locally
called porphyry, steatite, talc, etc., but really, I think, being a variation
of one of those massive muscovites which have been grouped together
under the general name of pinite. Chlorite is also almost always pre-
sent, even in the hardest portions of the stone. Tourmaline occurs
sometimes in large quantities, but more often in the normal tinstone it
is absent. Fluorspar is apparently always present ; it occurs somewhat
sparingly as the filling of small veinlets running through the stone,
though occasionally it is met with in larger masses. Of the metallic
constituents, tin oxide (cassiterite) is the most abundant, and the only
one of commercial importance. It occurs in fine grains and crystals
throughout the stone. Besides this, we find in small quantities blebs
of galena, black zincblende (marmatite), chalcopyrite, arsenopyrite, and
pyrite, distributed through the stone. These minerals also occur in
small irregular veins and patches, and one case is recorded in which a
considerable mass of argentiferous galena, assaying 80 oz. of silver to
the ton, was found in the tinstone at the surface. The component
minerals are not evenly distributed throughout the tinstone ; often it is
composed entirely of granular quartz, and, as a rule, quartz is very
much more abundant than any other mineral. After quartz, chlorite
is the most regular constituent. Pinite occurs sometimes distributed
evenly through the stone, at other times in irregular patches, in which
case it is often highly tin-bearing. Topaz is apparently absent.
Genetically, the. tinstone is clossly allied to greisen, but as mica is
absent I think it advisable to retain the miner's term, tinstone. The
German miner has the convenient term 'z witter' for such stone, but I
am not aware of any English equivalent. The term tinstone must not
be taken to imply that tin is necessarily present in payable quantities.
I believe it will always be found to contain some tin, but the tin
content may fall so low as to become practically indeterminable by
ordinary methods.
" The boundary between the tinstone and the granite is not marked
by any defined wall ; there is rather a passing over from the one to the
other, though this cannot be said to be gradual, since it takes place
within the space of a few inches. The stone in the vicinity of the
granite is apparently alwajs poor in tin. From the nature of the
boundary existing between the two rocks only one conclusion can be
arrived at, namely, that the tinstone is a product of the alteration
of the granite. This conclusion is abundantly demonstrated by an ex-
amination of the mineralogical and structural character of the tin-stone."
Mount Rex.
Mount Rex Tin Mine, about five miles N.W. of Avoca, is the most
important mine in the Ben Lomond district.
TASMANIA. 109
The mine is situated near the boundary of the granite and green-
stone. Towards the north the granite is overlaid by horizontal layers
of granite wash and sandstones of Permo-carboniferous age.
The granite is composed chiefly of quartz and felspar, with tlie
latter often developed in large crystals. Several tin-bearing formations
are known on the Company's sections, the most important at present
operated on is about centre of Section 1191-87 M. It consists of a
large mass or chimney of tinstone from 60 to 80 feet in diameter.
The shape of this deposit is very irregular, and the horizontal sec-
tion shows it is very different at the two levels. It has an approximate
strike of north and south ; at the upper level it is a little west of north,
and the lower level a little east of north. The general strike of all the
tin lodes in the district is west of north.
Small quartz veins traverse the ore body with a general strike west
of north, and small veins of fluorspar run through the stone having no
defined strike. This deposit may be regarded as a lens-shaped zone of
impregnation in the altered granite. Besides tin the ore contains a
little galena, copper and iron pyrites, and zinc-hlende. This ore
requires calcining, and the presence of a small amount of lead consti-
tutes a considerable metallurgical difficulty.
This deposit is of an unusual character, and the method adopted for
working the same is of interest. A large chamber has been excavated
at the 80-feet level, and the ore taken out here averaged about 7 per
cent, of black tin ore. A shaft has been sunk south-east of the deposits
to a depth of 142 feet, and a cross-cut ha& been driven across the
deposit, which is over 74 feet wide at this point.
The tin contents are by no means uniform, rich bands and patches
occurring besides poor ones ; the bulk of the tin is contained in the hard
quartzose tinstone ; the same sort of ore has been worked by the Great
Eepublic Mines, about 2 miles north-west, to a depth of 450 feet, and
there seems no evidence why the ore shoots should not live to great
depths in the district.
In the upper portion of the Mount Rex deposit a considerable
quantity of galena was found. This galena was probably of secondary
origin, and the percentage of galena has decreased as depth has been
attained.
About 7 chains north of No. 1 deposit another tinstone formation is
exposed, the ore being of the same nature as the first ore deposit
described above, and presenting many similar features. There are
several other ore bodies on which not sufficient work has yet been done
to completely determine their commercial value.
The Company has erected a 20-head battery and complete concen-
trating and calcining plant. The stamps have a weight of 1,100 lbs.,
crushing to 14 mesh ; the pulp passes through a pair of spitzlutens.
The former are treated in two compartment jigs, and the latter, after
further classification in spitzkastens, are treated on Wilfley tables. The
whole of the tailings pass over Munday's concave buddies, and the
slimes are treated in the usual way by settling pits and frames.
The zinc and the copper present in the ore are leached by means of
110 TIN DEPOSITS OF THE WORLD.
dilute sulphuric acid. Lead, however, owing to the insolubility of the
sulphate, cannot be got rid of by this method.
Tin Deposits in the Avooa Tin-Mining District.
There has been a considerable amount of mining done in this
district, the alluvial deposits being of secondary importance to the
lodes.
To the south in the valley of St. Paul's River the geological struc-
ture of the country is rather complex; numerous dykes of diabase green-
stone occur cutting through the ojder granites and Permo-carboniferous
formations. Immediately beneath the greenstones, near the St. Paul's
Dome come the sandstones, mudstones and conglomerates of the coal
measures, which appear almost to completely surround the Fingal Tier
and in places carry seams of coal. Mr. A. Montgomery, in his Geologi-
cal Report to the Government in 1892 of this district, states that tin
ore exists in coal measures.
This interesting fact is given in the following account : — " On a Spur
to the west of Bayley's Marsh Creek the ridge of granite is crowned
with huge castellated blocks of Permo-carboniferous grits and conglo-
merates, 400 to 500 feet above the marsh. The lowest layers of these
beds resting upon granite is a boulder conglomerate containing water-
worn lumps of granite and quartz, and amongst these very much water-
worn tin-ore has been found. This is one of the oldest deposits of
alluvial tin that has been recorded within my knowledge. It goes far
to show that the tin lodes existed in the granite fonnations even in
Palaeozoic times, before the conglomerates were laid down as beds of
boulders, by the water of the Permo-carboniferous sea."
The Brookstead property near the St. Paul's Dome is traversed by
a number of tin-bearing lodes running W.N.W. and E.S.E.
The lode stuff is as a rule mainly composed of quartz, but a great
deal of tourmaline is also commonly present ; there is also more or less
mica, talc and kaolin in the quartz, and fluorspar is not uncommon.
Some of the outcrops are stained with oxide of iron. Tin ore occurs in
bunches and strings, and also impregnated through the veinstone, often
in fairly large crystals, but more commonly in pieces from the size of a
pea downwards.
The Brookstead Proprietary Company has done some development
work on these lodes and erected a small crushing and dressing plant, but
the result has not yet been up to expectations. A certain amount of
alluvial tin has been won from the small valleys in the hills facing the
St. Paul's river on the north, and there is possibly some payable
alluvial wash in the fiats near the river which may repay the expense
of dredging.
The Roys Hill Tin Mine, near the Brookstead estate, consists of a
greisenised zone forming the margin of a small granite, spur which rises
out of the Silurian strata ; the tin deposit here is of a distinctly patchy
character. Both here and at the Brookstead estate, work has been
carried on intermittently for want of sufficient capital.
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TASMANIA. Ill
Description of Briseis Tin Mine.
The Briseis Tin Mine, Ltd., and Brother's Home No. 1, are the
most important mines operating on the deep-lead near the Ringarooma
River. Thej have an area of about 200 acres east of the present
Ringarooma River at what is praetieallj the head of the lead.
The early history of these workings is somewhat interesting. The
lead was discovered and worked in 1872 by a party of miners, the shallow
alluvial proving highly payable, the necessary water being obtained from
the Cascade River ; the lead, however, proving of greater extent than first
anticipated, two other companies subsequently started mining operations.
This part of the lead from the engineer's standpoint must be regarded
as a whole, and the trial for many years to work it by three separate
companies caused difficulties and constant litigation. It was only
recently that the Briseis Company accjuired by purchase and arrange-
ment the working control of the whole area.
The overburden, according to Mr. W. H. Twelvetrees, is an olivine
basalt, in which the felspar is mostly porphyritic, and the ground mass
largely consists of small brownish crystals of augite. In some places
this has been subjected to decomposition, which produces a soapy material
containing some hard boulders. These vary in quantity in different
parts — from 25 to 50 per cent, of the whole, and in size from that of
road metal up to boulders of two or three tons in weight. In the highest
part of the Briseis Hill there occurs a hard core of solid columnar basalt,
the various layers of which have been used for paving the water races.
The following particulars were given to author by Messrs. Lake and
Currie, Engineers to the Briseis Company : —
In March, 1903, it was estimated that on the joint properties there
remained unworked 4,200,000 cubic yards of tin-bearing drift, which
was covered under 2,181,000 cubic yards of overburden.
The local water supply having proved quite insufficient to handle
economically such a vast quantity of material, the Briseis Company had
constructed a race for the purpose of bringing water for a distance of
over 30 miles. Some idea of the size of this race can be obtained from
the fact that since its completion it has delivered at the mine approxi-
mately 24,000,000 gallons of water every day.
The Briseis Company have two other local supplies of water, but
the quantity obtained from these varies within wide limits, according to
the rainfall.
Before it is possible to work the drifts to the best advantage, it is
necessary that tbe overburden should be completely stripped for a con-
siderable distance ahead of the working faces. It is to this work that
all the resources of tbe Briseis Company have as yet been devoted, only
a sufficient quantity of drift being sluiced to slightly more than cover
the Company's total outlays and expenditure.
Description of the Overburden, — This consists of two layers separated
by a bed of drift, which in most cases carries a little tin ore. The top
layer consists generally of basaltic soil containing hard basaltic boulders,
while at two points masses of solid columnar basalt occur. These form
112 TIN DEPOSITS. OF THE WORLD.
the caps of two hills, which are both being removed bodily, in order to
uncover the drifts lying below. The greater proportion of this over-
burden can be removed by water, but the rock and larger stones must be
removed by trucking.
Method of removing Overburden, — This is accomplished in the fol-
lowing manner : —
In order to under-cut the harder material and cause it to fall, and
thus become more amenable to disintegration, about 20 feet of the top
drift is removed along with it. The softer material and smaller stones
are gradually washed away through main and branch tail races kept as
close up to the faces as possible, while the larger blocks and stones are
allowed to accumulate until they destroy the efficiency of the water.
The nozzles are then diverted to other faces, while the accumulations of
stones are removed by trucking, for which purpose main and branch
tram-roads are also laid close up under the faces.
Nature of the Drift, — This consists mainly of coarse quartz sand,
generally white, although occasionally of a red colour. The drift is
generally very clean and easily removed, but in places bands of a stiff
pug occur, which cause a little trouble. This pug contains no tin, and
requires to be broken up and in some cases removed by hand. There
also occurs in places what is known as ferruginous cement. This con-
sists simply of drift cemented together by the infiltration of water carry-
ing iron in solution. The cement in places carries tin, but the quantity
depends entirely on the amount of tin in the drift before the solidifica-
tion took place. When the cement is found in rich drift it is probably
rich, and when in poor ground there is no reason why it should be richer
than the surrounding drift. The tin ore occurs in irregular bands or
layers of varying thickness. In places it is very nearly barren, and in
other places rich streaks of pure cassiterite occur. Generally speaking, it
may be accepted that all the drift contains a certain amount of tin, but
that the richness increases with depth until in the actual gutter of the
lead a very high percentage of black tin is found to occur. From the
peculiar nature of the deposit, it is impossible to estimate what the
average value of the drift will prove to be, or what total quantity of tin
is likely to be recovered. From past results, it would seem that a yield
of from 5 to 10 lbs. per cubic yard may be reasonably expected, but it
has now been clearly demonstrated that even a less yield can be worked
with a large margin of profit.
Method of working the Drifts, — These are worked entirely by
hydraulic methods. The drift is first washed down through ground
sluices, where all the tin contents are caught, while the lighter material
is washed away. When it is thought that a sufficient amount of tin has
been concentrated in any particular ground sluice, this is gradually
worked down to the sluice boxes and streaming sheds, where the tin,
which occurs in comparatively coarse grains, is easily separated from
the accompanying material. There are fortunately no troublesome im-
purities, and an average product containing 75*45 per cent, metallic tin
is obtained by this simple process. A considerable portion of the richer
drifts lie below the actual sluicing level, which is regulated by the outlet
TASMANIA. 113
of the Ringarooma River. Such drifts are raised to the necessary level
bv means of hydraulic elevators.
The following figures, which are the actual results obtained during
the first eight months of 1904, will give a clear idea of what is being
accomplished : —
During the period an average volume of 36,000,003 gallons of water
was delivered at the mine from the various races : a total quantity of
495,277 cubic yards of overburden was removed, of which approxiidately
13 J per cent, was solid matter, which had to be removed by trucking.
The average cost of this work, including all labour, stores and materials,
was 5'3d, per cubic yard, or, including the proportion of all general
expenses, salaries and administration, 6'48c?. per cubic yard. The total
quantity of drift sluiced during the period was 102,440 cubic yards,
fr.»m which 281 tons 12 cwt. of black tin were recovered, or 6'1 lbs. per
cubic yard sluiced. The black tin produced 206 tons 17 cwt. of metal,
equal to 75*45 per cent. The cost per cubic yard sluiced, including all
expenditure up to bagging the black tin in the tin-shed, was 6'6od. per
cubic yard, or £10 1*. per ton of black tin.
The Briseis mine produced 971 tons in 1905, as against 422 tons in
1904, showing an inclusive average yield per cubic yard shifted for the
first nine months of 1*94 lbs.
During the period the overburden removed has been the heaviest and
most solid on the property, while the confined nature of the sluicing
faces would not permit of the most economical work being accomplished.
In the Blue Tier, Tasmania district, there is a deep alluvial lead
locally known as Thureau's Deep Lead. The country rock from George's
Bay, the coastal port for this district to the Blue Tier, is all granite
except in one portion on the east where some slates and sandstone of
Silurian age occur. Except for this sedimentary strata, the lead is en-
tirely bounded by granite which crops up along both sides at various
intervals.
This deep lead is the old bed of the George's River in early Tertiary
times ; the western part of Tasmania must have been higher above the
sea level than now, and the bottom of this deep lead is probably 100
feet below the present sea level ; the Blue Tier Range must then have
been higher than it is now, as denuding agents have been at work wear-
ing it down unceasingly ever since, and the modern river valleys are
probably very much below the level at which the streams ran that
carried out the channel of the lead.
A great deal of work has been done on the surface, and some good
shallow alluvial mined, but no attempt has been made to work the deep
alluvial gutter that must exist in some portion of the lead. This would
require to be tested thoroughly by bore-holes before any extensive scheme
be undertaken, and it is doubtful if the superficial portions of the lead
could be profitably worked by hydraulic sluicing even on a large scale.
Heemskirk District — West Coast Tasmania. The chief mine here
is the Mayne Tin Mine.
The country -rock consists of Silurian sandstones and slates, traversed
in many places by quartz -tourmaline veins, which have hardened and
114 TIN DEPOSITS OF THE WORLD.
tourmalinised the strata in their vicinity. The contact of the Silurian
strata with the main mass of granite is situated some 20 chains north of
the section.
Tin ore was first found on the surface of the spur in the form of
floating nuggets. These soon led to the discovery that much of the
surface-soil and rubble was rich in tin, and eventually the source of the
tin was located by the exposure of the outcrops of several lode-forma-
tions; This is worked on a small scale. December quarter, 1905,
10 men turned out 1 1 tons of tin ore.
The Mount Bischoff Tin Mine is described in Chapter XV.
( 115 )
CHAPTER X.
TIN DEPOSITS OF WESTERN AUSTRALIA, NORTHERN
TERRITORY OF SOUTH AUSTRALIA, NEW ZEALAND,
AND VICTORIA.
Tin Deposits op Western Australia.
Tin (alluvial and lode) has been discovered in three widely separated
localities in this colony, viz., at the head of the Bow and Lennard
rivers, in the Kimberley district, at Brockman's Soak in the Pilbarra
district, and at Greenbushes in the south-western portion of the
Colony.
The last-named field is a comparatively recent discovery, and far
exceeds in value any other tin fields yet known in Western Australia.
The Greenbushes Tinfield, as defined by the authorities, is situated
on a fairly lofty tableland drained by the heads of Norrilup and Hester's
Brook. The highest point of this tableland is 900 feet above sea level,
and is crossed by the main road from Bridgetown to Doonybrook.
The surface of this tableland is hilly and broken, but to the south-
westward the creeks open out into large swampy flats, which are
drained by steep rocky channels into the Blackwood River. The field
is connected with the main railway system of the Colony. Tin-mining
in the Kimberley and Pilbarra (Marble Bar) districts has only been
carried out in a desultory manner, the climatic and other conditions
being very adverse to the undertaking of mining operations on a large
scale, and very few details are available. In the author's opinion there
is a very great future for tin-mining in these districts, but the scarcity
of water presents grave difficulties. Even on the Greenbushes field
in the south-west, where there is a good annual rainfall, water is none
too plentiful at certain seasons of the year, and operations are retarded
in consequence.
The value of the output of black tin for the year 1902 (the
last return available) was £39,783, the two producing districts being
H 2
116 TIN DEPOSITS OF THE WORLD.
Greenbushes and Pilbarra. This return must be considered highly
satisfactory in view of the facts that in 1889 the estimated value
of the ore exported was only £300, and that at the present moment,
owing to the wonderful gold discoveries of recent years, the tin-mining
industry has been more or less neglected. Nevertheless, there is a
future for tin-mining in this Colony.
The tin deposits of Greenbushes fall naturally into two distinct
categories : —
Superficial deposits : —
(a) Alluvial deposits.
(h) Residuary sand gravels, etc.
Deposits in country rock : —
(c) Tin-bearing granite.
(d) Tin-bearing dykes.
Alluvial Deposits, — These are found flanking the course of all the
existing watercourses. The alluviums do not attain any very great
thickness, but a fairly large proportion of tin has been derived from
these deposits. The whole of these modern alluviums are not tin-
bearing ; the richest seems to be that formed by Spring Gully and its
tributaries, where a great deal of work has been accomplished. The
deposit in Spring Gully consists of two distinct portions : —
(1) An upper, or " free dirt," i,e. loose gravel ; jind
(2) A lower, stiff, "clayey dirt," containing irregular bands of
detrital tin.
The free dirt, which varied from 1 to 3 feet in thickness and about
18 to 20 yards in width, proved exceptionally rich in tin. The
physical character of some of the tin shows that it can only have been
released from the parent rock in close proximity to where it is at
present found. No small portion of it has been derived from the
denudation of the granite belt, reticulated with tin-bearing veins, which
crosses Spring Gully from north to south.
Residuary Sands^ Gravels, etc, — In addition to the alluvial deposits,
by far the larger portion of the field is covered with a mantle of
variable thickness of sands?, gravel, and conglomerate. These deposits*
are not, strictly speaking, of an alluvial character, but owe their origin
to the decomposition in situ of the underlying rocks. The sands unite
in giving what is practically a uniform section, which consists of from
2 to 3 feet of peaty soil, succeeded by a very variable thickness of
white, gritty sand, carrying varying proportions of mica, tourmaline,
and occasionally tin.
One of the most noticeable features in the structural geology of
Greenbushes is the ferruginous conglomerate and gravel, the position
of which has been accurately delineated by the Geological Survey
of 1902. In its mode of occurrence the conglomerate presents one
important feature, viz., that it does not form a horizontal table-
land, but occurs at different elevations, and seems to have adapted
WESTERN AUSTRALIA* 117
itself to the original cootour of the ground upon which it originated.
The conglomerate covered a much larger area than it at present
occupies, and denudation has gone on to a large extent since it formed
part of one continuous formation. The thickness of the conglomerate
is nowhere very great, operations having shown that it rarely, if ever,
exceeds 20 feet. In some portions of the field this conglomerate
carries a certain quantity of tin. The ore, however, is not evenly
distributed throughout, hut s^ems to be concentrated in certain conipara-
tively isolated patches. The tin from this conglomerate cannot be
extracted by the ordinary process of washing without milling. Like
alluvial deposits, these residuary gravels and conglomerates are
evanescent, and can be exhausted.
Both the modern alluviums and the residuary sands, gravels, and
conglomerates have yielded by far the greater pi>rtion of the tin turned
out from Greenbushes. It by no means follows that the richness of
these is proof of e?:ceptionally rich lodes or veins beneath ; for, owing
to the extreme difficulty with which certain minerals are acted upon by
atmospheric agencies, they often remain to gradually accumulate in
much greater quantity than existed in the parent rock. It is to this
natural process of concentration that the richness of the superficial
accumulations of Greenbushes is due.
Tin-bearing Granite, — The tin-bearing granite consists of a
granite passing in places into a foliated and highly-micaceous granite,
with little or no felspar. This granite (greisen) contains tin, tourma-
line, zircon, garnet, etc., as accessory constituents. In some parts of
the field the tourmaline occurs in such quantity in the gneiss as to give
a distinctive character to the rock, and would be better described as a
tourmaline gneiss. This granite has been reticulated by a number of
tin-bearing veins, forming a stock-work, and many have already been
worked in the zone of surface decomposition as alluvial deposits. This
area is not, however, conterminous with the legal boundaries of the field ;
the continuation of the tia-bearing belt should be looked for in both a
north and south direction. The presence of the ubiquitous con-
glomerate, however, would render prospecting on the north most
difficult. The best localities to search for further deposits would be
along lines of greatest erosion, and that is in the vicinity of the present
watercourses.
Whatever doubt there may have been as to the occurrence of
ore deposits, other than superficial accumulations, has been definitely
set at rest. The ore bodies are not lodes within the strict meaning
of the term, but are merely a network of irregular tin-bearing veins,
distributed over a fairly well-defined area. Such deposits, which owe
their origin to deep-seated sources, are as likely to be as permanent as
anything in the nature of such ever can be. It, however, by no means
follows from this that any individual vein can be followed laterally or
vertically for any great distance, but each vein will give place to
another, and so on.
Owing to the extremely low assay values of many consignments of
what seemed to be perfectly clean tin ore which have been shipped from
118 TIN J?EPOSITS OF THE WORLD.
the district, attention has been naturally directed to the mineralogical
characteristics of the ore. It was found that associated with the tin
was a mineral of about the same specific gravity as cassiterite, rendering
it almost impossible to separate the two mechanically. These investi-
gations confirmed ' those made by Mr. G. A. Goyder, the Government
Analyst of South Australia, in 1893.
No wolfram or scheelite has been detected in the ore : the mineral
once thought to be the latter having proved in every case to be
stibio-tantalite. These minerals (a tantalite of antimony) and taotalite
are of the greatest interest to the miners and smelters, since it is
impossible to separate them from the tinstone by dressing, their specific
gravities being practically identical. They have therefore to be
smelted with the tin ore, and by contaminating the smelted tin with
antimony, etc., seriously affect the purity and value of it. Owing
principally to the presence of these two minerals, the dressed ore from
the alluvial claims has been found to be very variable in richness,
ranging from a trace only of tin up to 72 per cent.
A complete analysis of marketable ore assaying low in tin was
made in the Departmental Laboratory, with the following result : —
Loss on ignition '22
Tin Dioxide, SnOa - - - - ■ 53-14
Titanic Oxide, TiOj - , . . -67
Silica, SiOa 1-61
Ferric Oxide FcgOs 4-11
Alumina, AlaOj ----- -42
Manganese Protoxide, MnO - - - 1*61
Lime, CaO '69
Magnesia, MgO '39
Antimony Tiioxide, SbgOa - - - 15' 13
Bismuth Trioxide, BijOj - - - - Trace
Tantalic Oxide, TagOg - - - - 19.85
Niobic Oxide, Nb^Og . - - - 3-56
101-40
Metallic Tin 41*80
Owing to the fact that Antimony Oxide tends to form an extremely
impure tin alloy, a considerable loss of tin might result in refining.
Doubtless this drawback can be overcome when the properties of the
mineral (stibio-tantalite) have been properly investigated. The occur-
rence of this mineral may be held to explain why some of the returns to
the vendors oi tia ore have fluctuated so considerably.
Since the year 1891 mining has been carried out in somew^hat
desultory fashion, and, considering all things, a fair quantity of tin has
been raised, as disclosed by the records kept in H.M. Customs House.
These figures until quite recently were the only data available for
WESTERN AUSTRALIA.
119
arriving at the yield of the Greenbushes Tinfield, which is shown in
the following table : —
Export of Tin Ore from the Greenbushes Tinfield.
Year.
Ore Exported.
Estimated Value.
Tons. Owts. Qrs.
£ s. d.
1891
204
10,300
1892
265 9 3
13,843
1893
171 10
7,664
1894
371 5
14,325
1895
277 3
9,703
1896
137 5
4,338
1897
95 11
3,275
1898
68 2 3
2,760
1899
278 8 1
21,138
Total -
1,868 14 3
87,346
Since the year 1900 steady progress has been made, the amount of
tin produced during 1902 being 403 tons as against 321 tons in 1901,
an increase of 25 per cent.
Export of Tin Ore from Pilbarra.
Year.
Ore Expojjted.
Estimated Value.
1
Tons.
Cwts.
Qrs.
: £ s. d.
1893
56
9
3,470
1894
19
949
1895 )
1898 /
1899
29
11
2,025
Total -
105
i 6,444
Tin Deposits of the Northern Territory of South
Australia,
The northern territory of South Australia contains 523,620 square
miles, or 335,116,000 acres, and has been proved to be rich in minerals.
The Kev. J. E. Tennison Wood, in October 1886, furnished an
exhaustive report to the South Australian Government describing its
physical features, geology, and minerals. In this report he expressed
the opinion that tin will eventually be one of the great sources of the
mineral wealth of this region. No quantity of alluvial tin has been
found, but lodes carrying tin are numerous ; he goes on to assert that
120 TIN DEPOSITS OF THE WORLD.
the Northern Territory may be emphatically pronounced to be a tin-
country. The extreme aridity of this vast tract of country renders it
both expensive and difficult to prospect and open out. What the
result of the construction of a trans-continental railway from Western
Australia to the Port of Adelaide (now under consideration by the
Federal Government) through this great central desert would be is still
more or less a matter for conjecture, but that it would serve to open up
some rich mineral areas is the opinion of all who have explored the
interior of this little-known portion of Australia.
There is very little data available concerning tin-raining in the
northern territory. Mount Wells appears to be the most important
tin-mining centre at present. The Mount Wells Tin Mine, situated
between Yam Creek and the McKinley river, bears jjeologically a
resemblance to the tin mines of Cornwall. At the 230 feet level the
lode is over 4 feet wide, tin dressing and crushing machinery being
erected. The South Australian Government Geologist in 1904
reported that this lode is composed of brecciated quartz cemented by
oxide of iron, carrying a small percentage of cassiterite about 50 feet
wide, and seemed likely to continue in depth. The McKinley and
Mount Wells Tin Mining Association held in 1898-90 five blocks
containing about 3,200 acres. The tin occurred in fine crystals in
quartz, slightly stained with oxide of iron. Some picked ore sent to
England produced over 50 per cent, of tin. The Government Geologist
visited this field in 1894, and in his report stated that it had been
deserted by the white men.
Some years ago the Mount Shoobridge Tin Mine worked two small
parallel lodes. The main lode varied from 2 feet to 8 feet wide, and was
sunk on to a depth of 150 feet; some rich patches of ore were found,
the cassiterite occurring in quartz, the country rock being composed of
slates and schists.
In 1893 the Company completed the erection of crushing anl con-
centrating machinery, and crushed about fifty tons of black tin assaying
65 to 63 per cent, of metallic tin.
Tin minin;^ in the Northern Territory seems to have been morcj
flourishing about ten or fifteen years ago, the gold discoveries in
Western Australia and the gold discoveries near Arltunga (N.T.) having
led the miners to abandon tin-mining. The Northern Territory at
present offers few inducements for the white man to settle in it. It is
inhabited principally by Chinamen, Japanese and Malays. With better
transport facilities anl the advent of the Trans- Australian railway it
may yet become a certain factor in the tin production of the world.
The value of the tin exported in 1902 was £5,985, and that in 1903
£10,772, so that the industry cannot be regarded as being actually at a
stands ill.
Tin Deposits of New Zealand and Victoria.
Tin has been mined on Stewart's Island in the South of New
Zealand, but has never proved a commercial success, and at present the
NEW ZEALAND AND VICTORIA. 121
output is only nominal. The tin raised being won from shallow alluvial
workings in the small valleys near the base of the mountains, which are
mainly granite, no lodes or stockworks of any value have been dis-
covered, and the whole deposits may be regarded as commercially
unimportant.
Tin deposits of Victoria are the least important of any* of the Austra-
lian Colonies. Stream tin has been found in the Beech worth district,
and in 1880, 103 tons were obtained, but at the present day Utile or no
un worked alluvial tin drifc exists.
Various attempts have been made to work the numerous small tin
lodes known to exist in the Mitta Mitta valley, but none have been
attended with success up to date. In 1897 the author inspected a
number of small tin lodes in this district. The country rock was a
coarse-grained porphyritic granite, with the felspar crystals large and
well developed. The cassiterite occurred in irregular masses through
some of the small lodes which traversed the granite country but no
attempt was made to work them on a large scale. The general average
of the ore was too poor to pay ; when opened out the lodes were
proved to be most uncertain in depth.
At Mount Wells tin has been found in veins and disseminated in
granite, forming a true stockwork, and gave the promise at one time of
being a paying proposition. The best year for the production of tin
was 1891, the output being 1,778 tons valued at £5,092, but it has
sunk practically to nothing at the present time.
* In the Beechworth district payable alluvial tin ore has been found,
several samples assaying up to 12 per cent. A number of miners are
engaged in washing the alluvial for stream tin in all the gullies and
little creeks falling from both sides of the range.
* "Mining Journal," Oct. 20, 1906.
( 122 )
CHAPTER XI.
THE TIN DEPOSITS OF BOLIVIA.
*The tin-producing districts of Bolivia are situated on the Eastern
Cordillera of the Andes, between latitude 21° S. and latitude 16° S.,
extending north and south over a distance of 300 miles, appearing in
distinct groups. They are all to the eastward of the great Bolivian
plateau, in which are the lakes of Titicaca and Poopo. No tin mines
are known to exist in the Western or Coast Cordillera.
Geological.
The Andes in this district are of the Silurian series, and include the
rocks of both the Upper and Lower Silurian formation, abutting to the
westward on the old lake bed. The formation is of great thickness in
the valley of the Arque, at the foot of the mountain of Berenguela, a
height of 6,000 feet above sea level. Nearly the whole stratification
can be seen plainly up to a height of 14,000 feet, and it is the same up
to the summit of Tres Cruces, at the height of 20,000 feet.f
This range has been disturbed by eruptions of porphyritic rock,
which shows plainly in isolated groups of hills, such as Oruro, Sicasica
(Garce Mendoza), and others, which formed islands in the great lake ;
these porphyritic rocks are the chief feature in this range. Prior to
these eruptions of porphyry has been the intrusion of the granite, which
is abundant in the eastern ranges, but is more seldom seen in the main
range.
These eastern ranges consist of slate or layer upon layer of grey-
wacke, shales, and thick beds of sandstone ; they are generally aurifer-
ous. Further to the south the eruptive rock is trachyte, and near to
Chile and the Argentine Republic the rocks are gneissic, or schists
broken up by granitic intruf?ions.
On the western side of the lake-bed the formation is distinct with
rocks of the oolitic series, with a belt of Permian formation, in which
are situated the copper veins of Coroccoro, San Bartolo, etc.
* Chas. S. Pasley, "Inst, of Min. and Met.," 1898.
f The cleavage in general is from north to south with the dip to the eastward,
most of the lodes cutting the stratification at right angles. This appears to be the
same ia the silver mines.
BOLIVIA. 123
There are scarcely any signs of volcanic action east of the old lake-
bed, except at La Paz, and earthquakes are unknown.
Nearly all the tin lodes occur in the porphyry, or altered andesite,
but in a few places the lodes run through slato and trachyte. The
veins iu the porphyry were geuerally the richest and of better quality,
the others being mixed with antimony, iron and copper pyrites, zinc-
blende, and sometimes with bismuth and wolfram. The tin usually has
traces of silver, and the lodes frequently have a capping of iron.
Mines.
The tin-producing districts may be divided into four ; Oruro in the
centre, La Paz in the north, Chorolque in the south, and Potosi further
to the eastward.
Gruro is by far the most important of these districts, the amount of
tin sent from Oruro being above two-thirds of the total production of
Bolivia. The following is a brief description of the principal mines of
the country, commencing with the hill of Huanuni — the most important
mines of the Oruro district.
Huanuni Hill. — The mountain of Huanuni has an imposing ap-
pearance, rising over 2,500 feet above the river which flows at its base,
and is about 15,500 feet above sea level.
The principal lodes run nearly east and west, dipping to the south,
cutting the strata at right angles in one part of the hill, and at an
angle on the opposite side. The stratification is very irregular, and
there are a number of faults. Four of the principal lodes run nearly
parallel, and have a dip of about 50° to the south. These lodes run
across to another hill of slate, their character changing with the different
rock, being mixed with arsenical pyrites. There are three or four
other cross lodes, but these are not nearly so rich — these cross lodes
seem to be of later formation.
There are several proprietors on this hill, the chief owner being the
Huanuni Company and a Bolivian firm. There are also about half a
dozen others.
The lode worked by the Huanuni Company, named the Catarecagua,
varied in width from 2 to 8 feet. The ore is fairly continuous through-
out, but has rich shoots. The Spaniards, who were former owneis,
worked down on one shoot to a depth of 1,000 feet vertical. This part
is now cut by a tunnel and worker! by more modern methods. The old
working is used for ventilation ; formerly the ore was partly sorted at
the bottom of the mine and then carried out on men's backs — a man
could only make two journeys in a day, carrying 75 lb. at a time.
There are signs of galleries in several places, but these were all blocked
up with the dirt carried up from below.
The tinstone is generally richer on the foot wall, but the tin is fairly
good throughout. Both the rock and the vein matter are very hard.
The sorted ore from the lo Je as a rule coataine J about 50 per cent.
124 TIN DEPOSITS OF THE WORLD.
of oxide, and the poorer stuff about 20 per cent. The ore picked over
by women, who g3nerally throw away any stuff containing less than
10 per cent., is hII put on one side to be worked at some future time
as there is sufficient ore of the richer quality to keep tlie floors goiug.
Tliis mine produced about 100 tons of concentrates per moutli.
Tuis company has a 10-stamp mill and several jigs and round
buddies, the floors beiug worked on a moJified Cornish system wlihih
was very successful. The tailings from the floors contained about
o per cent, of oxide. These were all saved to be worked over again.
The ores that were being sorted were extremely rich ; some of the
ore gave 65 per cent, of tin without concentration, and the dumps ran
about 15 per cent, of oxide. They had struck a very rich pocket in
soft ground, and had takea out 2,000 tons of concentrates.
Their work was all done on the old Spanish system — all the ore
and dirt being carried on men's backs, and the floors were managed in
the same fashion. The ore was washed by women in a narrow trough
about 12 to 18 inches wide. The bottoms of the troughs are made of
peat, with a curve so as to gradually lessen the force of the stream of
water. The ore is moved up against the water by a thin piece of wood
a little shorter than the width of the trough until the dirt has been
carried off.
This process is exceedingly wasteful, nearly all the slime tin being
lost. The ore was crushed by a Chile mill, worked by mnles.
Several of the other mines appeared to be important, but were
badly worked. The total production of the mines in this hill amounted
to about 250 tons of concentrates of 65 per cent, metallic tin per month.
Some of the lodes in this hill had a large quantity of pyrites, but these
were not worked.
Close to Huanuni at the base of the hill are several veneres or
deposits of stream-tin ; some of these were worked on a small scale
on tribute ; the quality was very good, but the quantity produced very
small.*
MoROCOOALA. — Ten miles norih of Huanuni are the mines of
Morococala, VilacoUo, and Negro Pabelion, on hills of the same names.
At Morococala are three mines with different owners. The principal
one is worked by a shaft sunk on the lode, which is 12 to 15 feet wide
in places, and carries very rich and pure oxides,
ViLACOLLO, a short distance from Morococala, was abandoned, and
most of the workings had caved in owing to the softness of the
ground and want of timbering. Large quantities of ore had been
taken out of this mine in former years. The quality of the ore was
* The extent of the " veneres ' waa very large. These had been prospected by
the natives in various plact s, and the best patches worked. Tiiere was plenty of
water, but very little fall could be obtained. Some of the patches had too much
iron, but in many places the stream tin wa< in large rounded pieces weighing a
couple of pounds, and nearly pure oxide. No sy.-tem was observed in working the
stream tin — each man working where he pleased on tribute, and generally stealing
about half the tin that he obtaineiK
BOLIVIA. 125
bad, the percentage of iron heing very large. A caretaker, who had
worked in the mine, said that it was not a lode, but only a shoot.
There was no trace of walls ; the surrounding rock was sandstone of a
deep red colour, impregnaied with iron. All the dirt taken out of the
mine contained tin-stone mixed with iron oxide and pyrites. A shaft
of 250 feet had been sunk at the bottom ; there were no traces of tin,
the metal containing a little silver with arsenical pyrites. The floors
were three miles from the mine, there being no available water nearer.
They were of the native type with a large Chile mill for crushing.
Negro Pabellon, a mine owned by a German firm, and worked on
tribuie by a Chilian miner, was of quite a different type to the others
mentioned, the lode running north and south and vertical, and in the
same direction as the cleavage. The dip of the strata was about
45° E. The country rock was slate, and the lode contained the same
rock and tin-stone mixed with iron pyrites. The tin was very rich and
easily worked, the ore averaging 20 per cent, from wall to wall. The lode
seemed very regular, about 3 feet wide, crossed by several small veins;
rich pockets were encountered wherever the lodes crossed. The mine
had not been worked to a greater depth than 100 feet. The tinstone
was soft and easily washed and crushed ; the concentrates gave a very
high percentage of tin, up to 70 per cent.
The floors were of very small dimensions, as the water was verj*^
scarce, hand jigs, and various hand troughs for hand washing were used.
The crushing was done by a Quimbalete, or rocking stone. A short
distance from the mine were old floors with an iron overshot wheel for
drivins; a 4-sramp battery, but the water was not sufficient to turn the
wheel round.
The mines of Morococala and Negro Pabellon are about 15,000 feet
above sea level. In each of the watercourses between Huauuni and
Negro Pabellon wtre found one or two people washing stream-tin.
The principal venero was at Japo. This, stream tin was in pa-tches
and of good quality, but there was very little water in the streams.
The natives who work in this way are quite contented if they collect
and sell 1 cwt. per week per man, but very often these stream-tin
washers will collect about 10 to 12 cwt.
CoLQUiRi. — Fifty miles to the north-east of Oruro are the mines of
Colquiri. They are situated in the province of Inquisivi, which officially
belongs to La Paz, but it is over 100 miles from that town. The
principal lode, which is of great width, was worked by the Spaniards
for silver chlorides. The deepest working that was discovered by the
author was 175 feet from the surface ; this reached the water level.
This lode can be traced for 3 miles on the surface, having immense
" desmontes," i.e. dump?, all the way along.
There is a tunnel about 1,000 feet long cutting the lode just above
water leve', and in another part an adit nearly as long. The vein
matter is 80 feet wide in the tunnel. The walls are well marked and
vertical. The lode runs N. 80° E. and S. 80° W. The tin on the
126 TIN DEPOSITS OF THE WORLD.
south wall had been worked on either side for 150 feet, and had been
stoped out up to where it was covered by the silver chlorides. The
tin had apparently been in pockets, as the width of the workings varied
from 2 feet to 10 feet. By the books the people who had worked it
had sent away over 500 tons of concentrates. The author found
specimens that were mixed with pyrites that gave 75 per cent, of oxide.
Beyond this streak of tin the vein matter consisted of arsenical pyrites,
magnetic iron, copper pyrites, heavy spar and iron oxide, with narrow
veins of galena about half an inch wide, dipping across the other vein
matter to the north. These galenas contained about 100 ounces of
silver to the ton. Beyond these, next to the northern wall of the lode,
was a wide streak of grey clay mixed with iron pyrites in large lumps
with tin and fluorspar disseminated throughout the clay. Water was
filtering through this streak, which averaged 8 feet wide. It was expen-
sive to work and had been abandoned, as the stone arch work was too
expensive to build. The tin stuff averaged 4 per cent. A shaft had
been sunk in the middle of the lode for 75 feet. This was full of
water, which could not be handled without machinery. The water that
ran out of the tunnel was used for washing on the floors. An analysis
of this gave 1 J per cent, sulphuric acid, and 1 per cent, of copper. The
ores were first concentrated to about 40 per cent., and then roasted in a
reverberatory furnace and re-concentrated.
Twenty miles north of Colquiri is the Tres Cruces, a large group of
mountains 20,000 feet high.*
The only tin lode worked was Sayaquiri. The lode was about
25 feet wide ; the tinstone was mixed with iron pyrites, and also con-
tained wolfram ; wherever any sinking on the lode had been done the
tinstone got worse in quality. This lode ran E. and W., and was
nearly vertical ; in other lodes the tin was remarkably pure, in brown
coloured crystals, the concentrates giving 70 per cent, of tin, but these
veins were at a great height, far from water, and snow-covered half the
year.
Here was found a large block of nearly pure oxide, about 2 feet
thick, among the detritus at 18,000 feet. The lodes contained tin
mixed with antimonial silver, running at nearly right angles to veins of
gold-bearing quartz, but one could never see the actual place of crossing
or where they had been cut off ; also this part was too far from the
railway, 85 miles by road, making the freights too high.
The mines of Oruro are well known as silver mines ; most of the
lodes have tin on the surface, which sometimes penetrates to a con-
siderable depth, mixed with the silver ores. All the work is carried
on for silver, no account being taken of the tin until the silver has
been extracted by amalgamation (with the exception of a few con-
tractors who work the tin stuff found on the dumps and close to the
surface).
There is no water at Oruro available for floor ; the ores are carted
* All the tin lodes in these hills were at the southern end ; in the eastern side
all the veins were silver and galena, and to the north auriferous quartz.
BOLIVIA. 127
to the amalgamation establishments about 15 miles off. There are two
of these, " Maehacamarea " and " Obrajes."
The tailings of the silver ores are washed for tin ; about 50 tons of
concentrates are obtained monthly. The tin is not of good quality and
is very variable in quantity. It is nearly all worked on tribute. Frue
vanners were used for concentrating.
At Oruro there are several large deposits of slags left there by
Spaniards who smelted the Oruro ores for silver ; these slags contained
30 per cent, of tin and 20 per cent, of lead and some silver. A quan-
tity was shipped to the coast to be re-smelted, but did not pay.
At the mines of Challa-Apacheta, 12 miles south of Huanuni,
which were worked for some time by a Cornishman, there is another
curious instance of a very wide lode, which is about 120 feet wide with
the tin in patches, the vein matter consisting of clay and iron oxide,
the tin being principally slimes. All the tinstone was mixed w^ith
arsenical pyrites and iron oxide ; the vein matter was very soft and
could be worked with picks. The tin averaged about 2 to 3 per cent.,
but was easily worked. The slimes were of very good quality. When-
ever a good-sized hole had been made a cave-in would take place, and
the dirt was wheeled out to the floors until no more dirt would fall.
There were workings on one side reaching a depth of about 100 feet.
The ore here was very dirty and of bad quality ; the lode appeared to
be changing into pyrites at this depth.
The floors were worked by the Cornish system with square buddies
and kieves. There was a scarcity of water in the dry season.
The Mines op Abicaya. — About three miles to the south east
of this mine is the hill of Challa Grande, with the mines of Abicaya,
Totoral, and Chuncho.
The veins in the two first named run east and west nearly parallel,
varying in their dip from 60° to 40° to the north.
The lodes are all in very hard porphyry, the tinstone being very
pure on the foot walls, but sometimes on the hanging walls, witn shoots
of ore occasionally from side to side, the veins varying from 1 foot to
5 and 6 feet wide ; all the vein matter was very hard, and had a lot
of quartz with it. The tinstone was sometimes in fair-sized black
crystals, but generally in compact masses. The tinstone taken from
the walls averaged 40 per cent., and the rest of the vein 20 per cent. ;
the lodes were all well formed and very regular. These mines are
situated on a spur of the hill, one on each side, Abicaya being
400 feet lower than Totoral. Chuncho is still higher and near the
centre of the hill. The lodes here run north-east and south-west, and
are vertical crossing the lodes of Abicaya and Totoral. The tinstone
in these lodes was softer, but more mixed with pyrites and iron oxide.
The floors of Abicaya consisted of a Gruson ball mill, a three-
compartment jigger, and a Frue vanner, which seemed to suit the class
of jnetal fairly well. These were driven by a turbine ; this could only
be run half time during the dry season. The floors of Totoral consisted
of Cornish jigs and square buddies, the ore being crushed with rocking
stones shod with iron.
128 TIN DEPOSITS OF THE WORLD.
Further ia the interior, about 30 miles east of Abicaya, are the
mines of Uncia and Llallagua, both on the hill of Uocia. The road of
Llallagua runs east and west and nearly vertical. The mine was
baJly worked ; the tinstone was rich and of good qualify, occasionally
mixed with pyrites, and often occurring in masses of large crystals.
The lode contained a large amouat of oxide of iron ; the ground was
soft and easily worked ; the floors consisted of square buddies, with a
rocking stone for a crusher.
At Uncia the mines were worked on tribute ; the lodes were wide
and well formed ; one of them, a cross lode, had an adit about 300 feet
in length ; the tin was mixed with silver and copper pyrites.
Further in the interior, about 70 miles east of Oruro, are the
mines of Berenguela in the mountain of the same name. These mines
are the furthest east of the Oruro district. The lodes, of which there
are several, are wide, apparently running north-east and south-west
with a dip to the north. The mouths of only two of the miues were
visited by the author, who had to judge of the others by the lines of
"desmontes." The tin stuff is nearly all in slimes, and ran about 6 to
7 per cent, on an average, and of very good quaHty. The hill is
exceedingly steep ; the mines are nearly 13,000 feet, whilst the valley
at the base of the mountain is 7,000 feet above sea level. On one
side of the hill there were masses of purple porphyry, and lower down
several spurs of the mountains appeared to be of red sandstone. Trees
grew wherever they could get sufficient hold, and water, both for
washing and power, was more than enough. These mines belong to
the department of Cochabamba, their outlet being by Oruro.
La Paz. — The mines in the La Paz district are not of great im-
portance ; one of them, Chacaltaya, had a wide but very uncertain
lode, and had floors consistiug of a Huntingdon mill, jigs, Frue vanners,
etc., driven by a Pelton wheel ; but the tin production was insignificant.
The most important mine was that of Milium. The work was left
almost entirely to tributors, who had been allowed to ruin the mine.
There were several small workings on the hill of Huayna Potosi ;
these were at the snow level, and were not visited by the author. The
whole tin production from the La Paz district is slightly over 300 tons
of concentrates a year.
* Chorolque mountain is situated in the south of Bolivia (about
21° S. and 66° W.), on the boundary line of the provinces of North
and South Chichas, in the department of Potosi. Its highest point
is nearly 20,000 feet above sea-level. The mine is worked at an
altitude of nearly 18,000 feet, and Santa Barbara, the site of the con-
centration works, is about 16,000 feet above sea-level. A good mule
accustomed to the high table-land of Bolivia can get right up to the
mine, along a rough zig-zag path, with perhaps even less fatigue than
a llama. The peak is generally more or less snow-capped, except in
the month of November, when for a short time a little ice is visible.
The south of Bolivia is noted for prevalence of high winds, and the
* Malcolm Roberts, "Inst, of Min. and Met.," 1901.
BOLIVIA. 129
heights of Chorolque are never free from wind, which at times is so
strong as to make the working x>f the wire ropeway impossible, as the
cars are blown off. During the rainy season there are great electrical
disturbances. The distance from the nearest railway station; — Uyuni,
of the Antofagasta-Oruro Railway — is 30 leagues. Thence to Quechisla,
4 leagues from Santa Barbara, carts can travel ; but between the latter
two places there is only a mule track, on which the upward journey is
very hard work.
. "There appears to be no other valuable mineral, at least to any
notable exteut, in the mine at present working, than cassiterite.
" The mine belongs to Araniayo, Francke & Co., and through the
courtesy of their representatives I obtained access to it. The work-
ings are at a great altitude, most probably because the lode lower
down does not contain tin. The mode of working is by means of
adit levels driven on the lode, connected by winzes or ore-passes.
The lode runs east and west, with a slight but variable dip to south,
crossing the precipitous southern face of the mountain ; its outcrop has
suffered great denudation. It is generally about 3 feet wide, and often
half of this is rich tin-ore ; but at times it pinches into streaks, which
frequently carry pretty crystals of cassiterite on one side and quartz
crystals on the other. It has numerous little branches or leaders,
which may be well mineralised for a short distance and then die out.
The walls are not well defined. The richest point seen was the deepest
in the mine, at the bottom of a winze over 300 feet from the outcrop.
The tin-stuff sent from the mine to the concentration works contains,
as far as I could ascertain, never less than 25 per cent, of metallic tin.'
No heed is paid to the numerous subsidiary shoots from the main ore-
body ; they are broken and used merely for filling the depleted stopes.
One cannot help suspecting that these off-shoots must to a certain
extent be impregnated with mineral, and that the filling must contain
a fair average percentage of tin. I did not see any systematically
prepared stoping ground. Probably through the richness and constancy
of the main lode no detriment arises from lack of development work
kept well ahead of stoping.
" An interesting project in hand is a cross-cut to the north to open
up other lodes which are believed to exist.
" The cold in the mine is intense, and this prevents the men from
idling. Though an end may be deficient in ventilation, which in other
mines would cause an unpleasantly high temperature, here the gallery
is glazed with ice. The ore on coming out of the mine appears very
dry, but exposure to the sun on the way to the concentration works
renders it a wet mass through the thawing of the ice.
" Works. — The ore is taken down to the concentration works on a
wire ropeway with two intermediate stations. The works themselves
are small, and embrace ball mills and jiggers. A windmill is about to
be used for power. There is no classification, and apparently no treat-
ment of fine stuff. Not long ago the grinding was done by rolls,
followed by good classification before jigging. Why a ball mill without
classification should have taken the place of the former installation is
130 TIN DEPOSITS OF THE WORLD.
not easily understood. Grinding dry in a ball mill must produce a fair
proportion of fines, and one would think that with such rich ore (25 per
cent.) fine grinding would serve no purpose, and that rolls would be
preferable.
" The dry-ground stuff is dropped into the running water of the
jigger, and much slime must float away. I have reason to believe
that the waste dump contains 3 to 4 per cent, of tin, and therefore is
about as rich as the Dolcoath lode. It will probably be re-worked in
the future ; but the slimes from the jiggers can never be recovered.
The ore is dressed up to about 60 per cent, metallic tin, and in that
state is exported as ' barilla ' to Europe. The maximum production is
5 tons daily.
" Only within recent years has any practical attention been
paid to the alluvial deposits. Work is now carried on for miles
by private persons on a small scale in all the quebradas or gullies
leading from the peak. The richest and at the same time almost
unique occurrence is called the ' Salli.' This is formed of immense
heaps of debris at the immediate foot of the watercourses of the steep
southern face of the peak. These heaps had their origin in the out-
crop of the lode, and they convey a good idea of the tremendous disin-
tegrating agencies at work here, and of the enormous denudation which
the lode must have suffered. Although these heaps are at no great dis-
tance horizof.tally from the lode, they do not form part of the possessions
of the mine. They were being worked by private individuals in the fol-
lowing manner : — The tin-stone is picked out of the heaps by hand, and
taken a short distance on the backs of llamas to where there is water.
Part is hand-broken and selected, and gives 60 per cent, tin ; the
remainder, after breaking, is ground by hand under big stone&
(trapiches\ then washed in a jigger to 50 or 60 per cent, and exported ►
The gullies in the rainy season are torrents at times, so that great
lumps, weighing some pounds, of almost pure cassiterite are carried from
these heaps, and are met with miles away. The loose bed-stuff of
these gullies, not counting boulders, for a distance of 4 miles contains
up to 3 per cent, tin, and the hillsides ^ per cent. Work is done in a
very primitive fashion, and is confined to the beds. Holes being made^
the larger tin-stones are picked out at once by hand, and the smaller
material is put into a sort of sluice or box about 6 ft. long. Probably
even by this crude method of washing not much tin is lost, because,
owing to the steepness of the gullies, all fine tin must be swept down
to the rivers. The dirt on the hillsides, fairly extensive in some
places, has not been worked as yet, and it will probably remain un-
touched for a long time^ because the torrent beds form natural concen-
trators, and receive fresh supplies during every rainy season. The
difficulties of working on a large scale are want of capital and of men,
and particularly the natural difficulties presented by the paucity of
water and the cold climate. During seven months of the year little
work can be done, as the water is frozen, and only for a few hours
daily does it thaw sufficiently to give a stream and permit working..
The summer months, when it rains, have to be relied on for outputs
BOLIVIA. 131*
These deposits at present do not produce more than 25 tons of
' barilla ' per week, so that the total output of the Chorolque
district is about 175 tons of 'barilla,' or say 105 tons of bar tin
monthly. At La Paz I visited the recently discovered Kimsi Cruz tin-
mining region, situated at an elevation of from 15,000 ft. to 17,500 ft.
above sea level. Tin occurs here under totally different conditions from
those in Australia. The country rock is altered slate, with occasional
bands or seams of porphyry, conforming to the strata. The tin ore is a
mixture of cassiterite and iron. Copper pyrites occurs in bedded
deposits at times, forming a contact with the porphyry, but mostly only
forming a separate bed in the slate. A most peculiar feature is notice-
able in connexion with the value of the ore. That is, that the highest
mines — those, say, above 16,000 ft. — are richest, the tin contents, in
beds 1 and IJ metre in thickness, running up to an average of 10 per
cent, metal, whereas beds or lodes in lower country are worthless. One-
mine, the Monte Blanco, was recently sold to a Chilian syndicate for
£170,000 cash, a tall price for an undeveloped mine, and, in conse-
quence, owners are asking about ten times the value of any holding
showing any ore. It is probably a good field, and will be developed in
time, but climatic conditions are awful at that altitude. Only Indians,
born in the locality can work, all imported men being unable to do more
than just move about, on account of the rarefied air. Although the
district is well in the tropics snowstorms are of frequent occurrence,,
both in summer and winter. The native so-called miners are now
receiving 5 to 6 bolivianos a day (about 9s.), and the men are very
scarce at that. The mine owners, therefore, are endeavouring to
secure Government sanction to import Japanese miners, as being
hardy."*
PotosL — There are not any mines in the hill of Potosi that are
especially worked for tin. As at Oruro, the silver lodes are mixed
with tin near the surface. Most of the tin stuff is taken from the
dumps of the old workings by tributors, who sell it to a smelter ;
these snxelting works use water-jacket furnaces ; the bar is of very
bad quality, as the metal is very much mixed with antimony and other
metals.
The fuel used is charcoal and llama dung. The smelting pays well
as the railway is 150 miles off; a good quantity of bar tin is sent
from here.
Ten leagues from Potosi are the mines "of Porco. These mines
are not worked ; they were abandoned as the ore was too poor to work.
The tinstone ran about 7 per cent, on an average ; there were a number
of lodes, and the floors were worked by water-power.
To the north of Potosi are the Maraguas mines and the veneros
of Ocuri. The Maraguas mines were worked by fits and starts ;
they were not paying. The lodes, of which there were a great number,
were narrow and close together. The tinstone was rich. No proper
* *♦ Mining Journal," Sept. 29, 1906. An Australian's account of BoJivia'ft
mining industry.
I 2
132 TIN DEPOSITS OF THE WORLD.
work had been done to develop these lodes, as the work was done
by tributors.
The veneros of Ocuri were worked by two Cornishmeo, and had
given excellent results. The tin was plentiful and of very good
quality. There was plenty of water in the river, and the work was
carried on systematically. These veneres were a long distance from
the railroad— over 90 miles.
Many lodes exist in all of these districts which cannot be worked,
as they are claimed by people who never intend to work them. Any-
one can hold a mine on payment of a small fee and a yearly fee of five
Bolivian dollars — less than 10*. — a year per hectare. These people do
not pay the yearly fee after the first year ; but if anyone else claims
the mine the result is a lawsuit, which may last for years.
The progress made of late years in the tin-mining industry is due
chiefly to the completion of the Antofagasta and Bolivia Kail way
which was opened to Oruro in 1892. This has lessened the freights
and thereby enabled many people to start work ; formerly all the traffic
was carried on by mules, donkeys, and llamas from Oruro to the port
of Arica in Peru. Before the opening of the line the cost per cwt.
used to be : —
By mules in 5 to 7 days - - - about 10*.
By donkeys in 12 days - - - „ 8*.
By llamas in 30 days - - - - „ 5*.
It is now about 2s, 6d, per cwt. in three days by rail. The difference
with regard to machinery is still greater, as formerly all parts had to
be made for mule transport.
The smelting of the ores up to the present is not on any large scale.
The ores smelted at Quechisla from the Chorolque mines would pro-
bably pay as well if sent away as concentrates, and the ores smelted
in Potosi are those of very bad quality, the concentrates being so dirty
that no merchant would purchase them, except at a very low figure ;
for this reason the smelters buy them at a very low rate, and make
money by saving on freights. The railway company charge double
freights for all goods sent from the coast. The cost of coal, chiefly
Australian, is about £8 per ton delivered at Oruro — a prohibitive price
for smelters. The object of the railway company is to secure as much
freight down to the coast as possible.
Workmen are easily obtained, though they are not as plentiful as
formerly. Most of the mining is done by Cholos, Le. half-breeds.
Indians can be obtained for outside work, building houses, making
ditches, etc. They are not as highly paid as the Cholos, and are much
less trouble to look after.
These districts are all at a very high altitude, and are very healthy.
As a rule Europeans soon become accustomed to the rarified atmo-
sphere, and live perfectly well at 16,000 ft. From May to August the
cold is intense, the thermometer often falling below zero (Fahr.) The
differences of temperature are very trying at times. The thermometer
BOLIVIA.
133
has shown 70° in the sun, and 10° of frost in the shade, as there is
hardly any radiation at these heights.
No. of
Location.
Name of mine.
lodes
working.
Direction.
Dip.
Rook.
Huanuni Hill -
Catarecagua -
B.&W.
50 S.
Porphyry.
M JJ
Barreno -
N.75E.
60S.
}}
11 11 "
San Jos^ -
N.80E.
45 S.
n
♦ 1 M
Dejada -
E. &W.
50 S.
11
(Penny Bros.) -
Vetilla -
E.&W.
70S.
11
11 11
»i " "
N.70B.
—
11
11 11 "
Various -
—
—
—
n
Negro Pabellon -
Negro Pabellon
3
N.&S.
(2 cross
lodes).
Vertical
Slate.
Morococala
—
3
B.&W.
})
Porphyry.
Vilacollo -
Vilacollo -
1
—
SandstODe
and slate.
Colquiri -
Socabon Verde -
1
N.80E.
Vertical
Slate.
Tres Cruces
Sayaquiri
1
E.&W.
»i
Porphyry.
Oruro
Various -
—
—
11
Challa Apacheta
Challa Apacheta
1
N.45B.
Vertical
Slate.
Challa Grande -
Abicaya -
4
N.SOE.
50 N.
Porphyry.
11 11
Totoral -
4
N.80E.
50 N.
11
11 11 "
Chuncho -
3
N.E.
Vertical
M
Dncia
Uncia
2
N.80E.
}}
11
» " ■
Tilallagua
1
E&W.
11
and slate.
Berenguela
Various -
—
—
—
Porphyry.
La Paz -
Chacaltaya
1
N.50E.
—
11
11 " '
Milluni -
—
—
—
Chorolque -
Santa Barbara -
1
E.&W.
Vertical
Porphyry.
Potosi
Various -
—
—
—
1)
The total production of tin in Bolivia, according to the yearly
statement of the Minister of Finance, takeu from the amount of export
duty paid, represents 5,910 tons of bar tin ; but in these figures the
conceutrates are not separated from the bar tin, so that the exact
figures cannot be given.
In the year 1893 the exports amounted to 2,000 tons, so that in
five years the production of tin has been trebled. These figures were
received after the author had made an approximate table of the amounts
produced at the various mines.
" The export duty charged is :
50 cents per 100 lb. of bar tin
35
concentrates
- 9d, nearly.
- Hd „
The author is indebted to Senor Avelino Aramayo, the Bolivian
Minister in London, for these figures.
134
TIN DEPOSITS OF THE WORLD.
Location.
Name of mine.
Height above sea
level.
Feet.
Monthly pro-
duction in tons
of Barilla.
Huanuni Hill
Catarecagua
14,500
100
■ j» »» ■ '
Barren - - -
15,000
»>
>> ij ' "
San Jose -
)}
II
ji 11 * "
Dejada
»»
II
»» »» " '
Vetilla
II
25
j» »» ■ "
Various
14,500
10
»> »» " *
Vetilla
„
15
Morococala
Various - - -
15,500
30
Negro Pabellon -
Negro Pabellon -
15,000
30
Vilacollo -
Vilacollo -
14,000
Colquiri
Socaben Verde -
M
10
Tres Cruces - - -
Sayaquiri - - -
15,000
10
Oruro - - - -
Various - - -
13,000
50
Challa Apacheta -
ChaUa Apacheta
14,000
5
ChaUa Grande -
Abicaya
15,000
35
»» »> ■ '
Totoral
15,500
35
>» jj * "
Chuncho -
II
—
Uncia - - - -
Dncia - - -
14,000
10
»»-•--
Llallagua -
13,000
35
Berenguela - -
Various
14,000
—
La Paz
Chacaltaya
15,000
25
>»""■"
Milluni -
14,000
25
Chorolque -
Santa Barbara -
16,000
35
Potosi - - - -
Various - - -
14,500
20
About 70 tons of bar tin is sent monthly from Chorolque and Potosi,
or about 6,000 to 7,000 tons yearly.
In the figures of production other small mines contribute ; these
figures are difficult to obtain correctly, as the owners are given to
• exaggerate the output of their mines, and tbe total of 7,200 tons of
barilla yearly of 65 per cent, of tin, equal to, say (with loss on
smelting), 4,650 of tin, counting the bar tin as 1,000 tons yearly, gives
a total of 5,650 tons.
Catarecagua, Huanuni -
Birreno - - - .
Morococala
Socabon Verde, Colquiri •
II i» II
Oruro, Salinas
Totoral, Challa Grande -
Uncia, Llallagua
I
Fe. I Oangue, &.o. ,
37-05
79-00
68-00
4-30
72-00
17-25
84-50
46-00
6-75
4-25
7-15
15-20
7-50
12-25
3-25
14-00
56-20
16-76
24-85
80-00
20 50
70-50
12-35
40-00
Average value.
Picked ore.
Traces of silver.
>> II
Picked ore.
Traces of silver.
Picked ore.
Traces of silver,
some antimony.
* According to Juan B. Minchin, the mining of tin in the vicinity of
Oruro, Bolivia, made considerable progress during the year 1903.
"The Mineral Industry," 1903.
BOLIVIA. 135
The outpat of tin concentrates or barilla for the year amounted to
3,721 tons, averaging from 64 to 71 per cent, metallic tin. This pro-
duction was divided among five mines, the largest of which is owned
by Abelli and Company, of Abicaya. The mine is opened by a shaft
of 95 meters depth, which is provided with a steam hoisting engine.
The ore is crushed in a stamp mill, and is then concentrated by jigs,
baddies, and Wilfley tables. The Huanuni mine has reached a depth
of 80 meters. The crushing machinery consists of a 10-stamp mill,
and its capacity is to be doubled by the addition of ten more stamps.
The Chuncho mine is a comparatively new enterprise. It is supplied
with a mill of 10 stamps. At the Uncia mine the ore is crushed in
part by small rolls and in part under rocking stone, and the concentra-
tion is effected with a Wilfley table, jigs, and round buddies. The
company is building a wagon road 45 mites long to the nearest railroad
station, and will erect a new plant near the mine. The Quinsa Crur
district, in the province of Inquisivi, has received a good deal of
attention recently, and important deposits apparently exist. Little
development work has been done as yet owing to the scarcity of capital
and defective means of transport. The mines of 'the district are
situated in the Great Cordillera, and have an advantage over most
mines of Bolivia, in that there is an ample supply of water for power
purposes.
* Tin Production.
The idea is prevalent that tin ore is superficial in Bolivia ; only
time will prove or disprove the correctness of that idea. In many cases
up to the present such is not true. Be that as it may, if there is no
further notable increase for some time in the output of Bolivian tin, it
will not be through want of ore in the lodes, but through scarcity
of labour. With the constant installation of new workings, the exten-
sive railway construction, &c., hands are getting more and more difficult
to obtain. If capital is not forthcoming to make automatic appliances
available, inside as well as on the surface of the mines, I am afraid this
labour difficulty will be practically insuperable for a long time to come,
taking into account the conditions — geographical, social, and political —
of the country : and, therefore, the greatest efforts in the Bolivian
mines are not likely to suffice to make any very appreciable impression,
in the near future, on the actual high price of bar tin.
The mining laws in Bolivia are exceeding liberal and good, but their
administration does leave a„good deal to be desired. This is undoubtedly
due in a great measure to a want of competent officials and proper
archives. In the past there has generally been such a lot of ground
vacant that there was room for all, without the necessity of great
exactitude in mining locations ; but now, when competition is becoming
* *' Mining Journal," Sept. 1, 1906.
136 TIN DEPOSITS OP THE WORLD.
rife, the Government must be impressed with this important matter of
correctly administering th€ law. A straightforward and good man as
Prefect of Potosi, to whom all mining petitions are directed, with
power to overrule opposition to such petitions in cases where the
objections are ridiculous, as some of them are, would in those cases save
a lot of time and trouble. Again, the Government must obtain com-
petent engineers for locating the concessions. Even at present, as
a rule, these are given or plotted by " peritos fiscales " with no know-
ledge whatever of surveying, and it can well be understood that in
hilly districts, such as almost all the mines comprise, a concession staked
with only a string or a tape is not liable to come out very exact ; so
that the best way at present is for every petitioner to have his claims
properly laid out and surveyed beforehand, leaving nothing for the
"perito fiscal" to do except quickly measure round to obtain his
conformity. Such is the procedure of every mining company here
which has an engineer. In time such conditions will disappear, their
existence being due chiefly to the shortness of Government receipts
which have not been sufficient to maintain the required number of
official engineers. At present law-suits should be avoided, and many
of them could be settled in the beginning, even if the opposer has some
reason in presenting his objections, by employing a little tact and a
trifle of money. In case a law-suit must be faced, the " via ejecUtion "
should be chosen, and not the " via ordinaria," as the obtainment of
judgments in the latter procedure might very well last a lifetime.
Bolivian Export Duties on Tin.
* The Board of Trade are in receipt, through the Foreign Office, of
a translation of a Bolivian decree fixing the export duties on tin ores,
leviable from January 1, 1907, at the following rates : —
Tin Ores,
If the quotation for Straits tin should be inferior Bolivianos.!
to £100, the quintal of 100 lbs. Spanish shall pay - 9*90
From £100 to £110 1-00
M5
1-30
1-45
1-60
1-75
2-00
2-25
2-60
3-00
3-50
no „
120
120 „
130
130,,
140
140,,
150
150,,
160
160 „
170
170 „
180
180 „
190
190 „
200
200 and above
* " Mining Journal," Nov. 3, 1906.
f Boliviano = Is. 7d. (nominal value).
BOLIVIA.
137
Tin Bars,
If the quotation for Straits tin should be inferior Bolivianos.*
to £100, the quintal of 100 lbs. Spanish shall pay - 1*50
From £100 to £110 1*60
1-75
1-90
2-10
2-3(T
2-50
2-80
3-10
3-40
3-80
4-20
In accordance with the quotation for Straits tin in Europe, the
Minister of Finance will fix fortnightly and with strict observance of
the preceding tariff, the rate of duty which the ores and bars shall pay,
which rates shall remain invariable during the fifteen days notwith-
standing that appreciable fluctuations in the quotation for Straits tin
may take place in the meantime.
Companies working tin mines are exempt from the contribution of
3 per cent, on their net profit hitherto levied.
* Boliviauo=l8. 7d. (nominal value).
)»
110 „
120
»»
120 „
130
>
130,,
140
>»
140 „
150
>»
150 „
160
»
160 „
170
5>
170,,
180
>»
180,,
190
)>
190,,
200
200 and above
(, 13S )
CHAPTER XII.
TIN DEPOSITS OF CORNWALL.
r
The Cornish mines afford the best examples of tin-lode mining for
the purpose of comparison, althoua:h too much reliance must not be
placed on the experience gained in any particular district ; still, the
knowledge obtained by observation and comparison of tin deposits can
be used when determining tbe value of newly discovered tin deposits
in many parts of the world. Much has been written by Mr. Henwood
and others on the Cornish tin deposits.
The lodes in Cornwall may be divided into the ordinary lodes and
counter lodes. Tin-ore occurs disseminated through granites, elvans,
and slates, as well as in minute veins in these rocks.
* Generally speaking, lodes which yield a mixture of the ores of
tin and copper are wider than those which contain ores of only one of
these metals. The lodes of Cornwall are wider in slates than in the
granite, and their average width is greater within 100 fathoms from the
surface than at any greater depth hitherto attained (subsequent develop-
ments at a depth have not borne out this statement in the Dolcoath mine).
Henwood furnishes the following figures as the result of his investi-
gations relative to the thickness of Cornish lodes : —
feet
Lodes yielding ores of both tin and copper average 4*7 in width.
„ „ tin ores - - -
-
3-0
„ ,, copper ores
-
2-9
„ in granite - - - -
-
3-1
„ in slate - - - -
-
3-7
„ at less than 100 fathoms deep
.
3-9
„ at more „ „ „
-
3-3
On passing from one rock to another, or from riches to poverty,
the width of a lode frequently changes, but under ordinary circum-
stances a lode commonly maintains, approximately, its characteristic
* Henwood, Vol. V., "Trans. Royal Geo. Soc. of Cornwall," 1839.
o
g
O
M
I?
o
m
o
S ^
ft s
s <
at p?
E§
PL4
CORNWALL. 139
breadth. The directions of lodes in the different mining districts are
not perfectly identical, nor are all those occurring in the same neigh-
bourhood strictly parallel.
The mean directions of the lodes in different parts of Cornwall are
given by Henwood as follows : —
St. Just - - - - 350 S. of E., N. of W.
St. Ives - - - - 8° S. of E., N. of W.
Marazion- - - - 1° N. of E., S. of W.
Gwinear - - - - 2° S. of E., N. of W.
Helston - - - - 16° N. of E., S. of W.
Camborne - - - 20° N. of E., S. of W.
Redruth - - - - 22^ N. of E., S. of W.
St. Agnes - - - 22° N. of E., S. of W.
St. Austell - - - 130 N. of E., S. of W.
Caradon - - - - 18° N. of E., S. of W.
Tavistock - - - 90 N. of E., S. of W.
Their average bearing is about 5° N. of E., S. of W., a course which
does not materially differ from that of the granite outcrops which at
intervals make their appearance between Dartmoor and the Land's
End, and also not unlike the course of a line drawn directly through
the centre of the county. Lodes present as many flexures in their
downward as in their horizontal direction, and vary in dip from an
inclination of less than 45° with the horizon to 90° ; the average
being probably about 70°. Sometimes, although less frequently,
lodes dip in opposite directions in different parts of their range.
Both lodes and cross-courses dip more frequently towards the granite
than away from it, and veins which maintain a nearly meridional
direction are in Cornwall more highly inclined than those coursing
more nearly east and west.
The most important tin-mining district in Cornwall is situated near
Camborne, and the geological conditions of this district are both
interesting and instructive. Mr. Donald A. MacAlister,* the Govern-
ment Geologist of Cornwall, who has spent some years in the examina-
tion and mapping of the Cornish tin deposits, writes as follows : —
t The lodes shown in the cross-section may, as far as they have been
explored, be divided into two groups ; those in the killas, on the north
of the section, have produced mainly copper, while those in the granite
mainly tin ; but they are all tin-copper lodes.
The lodes in this district appear to be influenced in the direction
of their underlie by the el vans, J while it is interesting to note the
remarkable change in the direction of underlie of the latter in glancing
* The author wishes to acknowledge the generous assistance given him by
Mr. Donald A. MacAlister.
t " Trans. Royal Geol. Soc. of Corn.," 1903. A cross-section and some Notes
on the Tin Deposits of Camborne, Cornwall, by Donald A. MacAlister.
t Robert Were Fox, " On Mineral Veins," " Rep. Corn. Poly. Soc. Falmouth,"
1836, p. 96.
140
TIN DEPOSITS OF THE WORLD.
I
I
w
'J
s.
A^VN* -aMtthtJ '
it
>'^
2
CORNWALL. 141
from one end of the section to the other.* It has already been pointed
out that "Granite, or its modification, elvan, occurs at or near all the
localities where tin and copper ores so abound."t We may therefore
say that in the Camborne area the lodes are ore-bearing fissures in the
vicinity of elvan dykes ; J from this point of view the ores must be
regarded as having been a later product of the same magma which gave
rise to the el vans.
General Geological Peculiarities of Camborne, — The main facts,
so well known, may be epitomised as follows :-^
The Palaeozoic sediments and the intrusive sheets of greenstone
were disturbed and metamorphosed in post-carboniferous times by
granite, § which has also penetrated them as sheet-like intrusions. |{ It
is certain that a great mass of sediment must have covered all the granite
bosses now visible at the surface.ir Shortly after the consolidation of
the granite, the elvan dykes were injected from the same eruptive
centre along planes of fracture, having a general bearing E. 30° N.
Then followed the period during which lodes were formed. The
greenstone is found at the surface in many places, and is the oldest of
the igneous rocks.
Mr. Teall** has referred to the apparent sequence of eruption from
basic to acid rocks.
Finally, cross courses, probably Tertiary, have faulted the district
in a N.N.W. direction.
The Mineral Lodes. — The formation of the lodes was the latest
phase of the plu tonic activity.! + They have the same general bearing
as the elvans, and are simple or bifurcating altered ore-bearing fissures
* De la Beche has already called attention to the apparent convergence of elvans
in depths, as if derived from the same source (" Geol. Rep. Cornwall, Devon, and
W. Somerset," p. 176). Some of the jointing in the granite appears to be subsequent
to the intrusion of the elvans, but proof is as yet wanting. See " Trans. Boy. Geol.
Soc. Corn.," 1901, vol. xii. part vii. p. 553.
JDe la Beche, •' Geol. Rep. Cornwall, Devon, and W. Somerset," p. 286.
See " Plutonic and other Intrusive Rocks of West Cornwall in their Relation
to the Mineral Ores," by Mr. J. B. Hill, R.N., " Trans. Roy. Geol Soc. Corn.,"
vol. xii. p. 688. Mr. Hill speaks of the coincidence of the general bearing of lodes
and elvans with that of the tough-way joints in the granite.
§ Mr. J. B. Hill, of H.M. Geological Survey, has touched on the possible lacco-
litic nature of the granite. "Victoria County History," Cornwall, Geology
section.
II W. J. Henwood, " The Metalliferous Deposits of Cornwall and Devon," " Trans.
Roy. Geol. Soc. Corn ," 1843, vol. v. p. 58.
U Estimated by Mr. J. H. Collins at 46,000 feet in thickness (" Geological Age
of Central and West Cornwall," " Journ. Royal Inst, of Cornwall," 1881) ; and by
Sorby (" On the Microscopical Structure of Crystals indicating the Origin of Minerals
and Rocks," "Quart. Journ. Geol. Soc," 1858, vol. xiv. p. 453) at 50,000 feet for the
Cam Menelez granite, or about 9J miles. The evidence for this very high estimate
is, however, not conclusive, but it is sufficient to show that an enormous mass of
sediment overlay the granite at one time.
** J. J. H. Teall, " Metamorphism in the Hartz and West of England," " Trans.
Roy. Geol. Soc. Corn.," 1889, vol. xi. p. 221.
tf De la Beche, " Geol. Rep. Cornwall, Devon, and W. Somerset," p. 310.
142
TIN DEPOSITS OF THE WORLD.
<
CORNWALL. 143
— frequently small fault-planes — in which the tin ore occurs as bunch
or pipe-like deposits, due to infilling of the fissure (so forming a leader)
and impregnation of country rock in its vicinity.*
The pitch of these ore bunches, in accordance with similar observa-
tions by Henwood,+ in other districts appears to be easterly.]: Sir
Clement Le Neve Foster found in Wheal Uny that no part of the lode
was absolutely barren, so that the pitch of the bunches could not be
determined.
Various writers § endeavoured to give different ages to the Camborne
lodes, but De la Beche assumed rather a certain period during- which
fissures would be open to fluctuating action.
Gaunter Lodes, — In the Camborne district there are at least a'dozen
caunter lodes, forming a distinct fissure system, having a bearing
approximately east and west. It seems that these lodes are really
subsidiary fractures contemporaneous with the main lode fissures. ||
(Fig* 26.) Although caunter lodes seem more prominent in the upper
AT
1 $0 Fn. LevcL
workings of mines, and in consequence of that position more often are
copper-bearing, they have, nevertheless, their deep-seated tin-bearing
representatives.il (Fig. 26.)
* De la Beche, " Geol. Rep. Cornwall, Devon, and W. Somerset," p. 317. Clement
Le Neve Foster, " The Tin Depc.sit^ of East Wheal Lovell : " " Trans. Roy. Geol. Soc.
Corn.," 1876, vol. ix. part ii. p. 8 ; " On the Great Flat Lode : " " Quart Journ. Geol.
Soc.," vol. xxxlv., 1878, p. 640.
t " Trans. Roy. Geol. Soc. Corn.," vol. v. pp. 54, 87, 193.
J At Wheal GrenviUe they are verv pronounced, and at Dolcoath the principal
ore body is coincident with the line of junction of the bifurcating main lode, and
the change in strike of the main lode near the caunter.
§ J. Carne, " Trans. Roy. Geol. Soc," 1822, vol. ii. p. 49.
ll W. J. Henwood. " Trans. Roy. Geol. Soc. Corn.," vol. v. pp. 253, 327. See
also Warington Smyth's remarks, " Physical Phenomena connected with the Mines
of Cornwall and Devon :" " Brit. Assoc. Rep." (Plymouth), 1877, p. 8.
H Cam Brea, Wheal Basset, etc. The Dolcoath caunter lode has been inter-
sected In the 220 fathom cross-cut, and Mr. Hosking (Tehidy Office) informs me that
it is now a tin-bearing lode of meagre dimensions.
144 TIN DEPOSITS OF THE WORLD,
Epitome of General Facts, relating to the Mineral Contents
of the lodes. — The copper ores of the ordinary copper-tin lodes occur
at a higher horizon in the lode than the tin; hence, in a lode traversing
granite and killas the copper is generally more productive in the killas
than in granite, although neither ore is restricted to those rocks
respectively.
When, as sometimes happens, leaders of tin and copper ores occur
side by side, the width of the lode is greater than usual.*
Gozzans characterise the upper parts of copper lodes, while in tin
lodes found outcropping in bared granite districts this peculiar feature
is less pronounced or entirely lacking.
Tin was, however, extracted by the old miners from the backs of
many gozzans.t The tin was probably concentrated by nature in the
back of the lode by the leaching out of the unstable copper sulphides by
weathering. Below the weathered zone various oxidised copper ores
were found, below which came rich sulphides of copper, so much so
that proportionately the tin present was reduced in many cases to an
insignificant by-product, while in depth the copper died out, and the
lode became a tin one. Henwood has already stated that the richest mines
are those situated around the granite margins. (Figs. 27 & 28.)
Notes and Conclusions. — The question as to the origin of our
mineral deposits in Camborne involves references both to primary and
secondary enrichments. The literature on the subject is extensive.
The depositions of tin ore in the Gligga Head granite has been
ascribed to pneumatolytic action. J Le Neve Foster, in a few classic
papers, described the processes of deposition which must have gone on
in our ordinary lodes. §
Primary Impregnation. — The elvan dykes were injected through
fractures in the solid granite, from a magma within which was still
viscous. At a later date those fractures connected with elvans were
more likely to have penetrated to greater depths than those found
away from elvans. Hence, after the consolidation of the granite, but
closely following on the injection of the elvans, !| they must have drawn
freely upon the sources of tin and copper, 1[ whereas the fissures and
* W.J. Henwood, "Address Roy. Inst. Corn.," 1871.
t J. H. Collins, " Sketch of the Geology of Central and West Cornwall : "
"Geol. Assoc," 1887, p. 20 ; " Origin and Development of Ore Deposits in the West
of England :"" Journ. Roy. Inst. Corn.," 1892. Many of the lodes in Gwennap
district had tin in the backs, while Cam Brea is an example in this district.
X Clement Le Neve Foster, F.R.S., "Trans. Roy. Geol. Soc. Corn.," vol. ix., 1878,
p. 213. Mr. J. B. Scrivenor, M.A. (H.M. Geol. Survey), "Quart. Journ. Geol.
Soc," vol. lix., 1903.
§ " Remarks on some Tin Lodes in the St. Agnes District : " " Trans. Roy. Geol.
Soc. Corn.," vol. ix. p. 185 ; "The Tin Deposits of East Wheal Lovell," id., vol. ix.
part ii. p. 8, 1876 ; " On the Great Flat Lode," etc. : " Quart. Joum. Geol. Soc,"
vol. xxxiv., 1878, p. 640.
II Near Gwinnear mineralisation is closely associated with the later of two sets
of elvans. E. Dixon, " Summ. Prog. Geol. Survey," 1901, p. 25.
U See also the remarks of Mr. G. W. Lamplugh (H.M. Geol. Survey) in " Eco-
nomic Geology of the Isle of Man : " " Memoirs of the Geol. Survey of United
Kingdom," p. 489.
CORNWALL.
14$
joint planes distant from el vans were not so easily, if at all, accessible
to the metal-bearing solutions. Yet some veins have manifestly been
open to action for longer periods than other?, as the wide-banded
" leaders," great thicknesses of " capels," or the lode breccias cementeil
by tin stone, peach, or quartz often testify.* Metalliferous solutions
''•W'*.' Mirrrewt
^ygw^^Hx^,^? ' 'y^ 'f^^^
ST. DAT TTNrrKO MIKES
''^iU\''.
Pia. 27
mHAfT SMArr
"ft^ ^tuof^ i£XtL- .' • '/*;*•
ufv^*:. ^y^^{ ^<<^^. '.
PEDN AN DREA
LON^ITT^OIJVAL SECTIOI^
35 FATHOMS*! INCH
FIG. 28.
* De la Beche, " Geol. Rep. Cornwall, Devon, and W. Somerset," p. 339 et seq^
See contribution by Dr. J. S. Flett (H.M. Geol. Survey), "Summ. Prog. GooJ^
Survey " 1902, p. 158.
146 TIN DEPOSITS OP THE WORLD.
from the interior of the granite mass* passed out through fissures
itowards its periphery, and impregnated the fissures mainly at some
•certain zone either in the granite or the killas,t according to the ther-
mal or other physical conditions.
The case of the Great Flat lode, with its exceptionally long " pipes "
of tin ore, is an example of prolonged infilling, due, possibly, to asso-
ciation with elvan. It has been described as a " contact deposit," but
strictly speaking it is not so, for this implies " segregation " from the
magma ; in fact, it is only at the junction of the granite and killas in a
very few places. In Wheal Uny, for instance, the lode in killas is at
least ten fathoms away from the granite in some places, while in others
it is wholly in granite (Fig. 24).
The question now arises as to what is the lower limit of the rich ore
ground. The precise boundaries of this cannot be defined, since they
are dependent on uncertain factors ; but experience has shown that the
lodes of this district are not uniformly productive to the deepest points
reached by mining, and although the rich ore zone in the Camborne
lodes is of great depth,! it is possible that exploration at deeper levels
will not provide so extensive a field for mining operations as was met
with in the upper levels. The change in the character of the ore from
being coarsely crystalline in the upper levels to fine and compact in depth
probably accompanies other changes in the lode. It is by no means
«uggested that the lodes become altogether barren, or that they lose
their peculiarities as cassiterite veins ; the occurrence of rich ore bodies
in depth is not precluded. The works of Vogt and Lindgren § do not
support any hypothesis which might suggest the total disappearance of
the ore in the deeper parts of the lodes. It can only be inferred, then,
that, generally speaking, the conditions assisting the deposition of
cassiterite from its solutions were more favourable near the periphery of
the granite than those nearer their source, and that solutions reaching
the cooler regions near the contact deposited the whole of that cassiterite
which they had managed to retain in the upward journey.
Allusion has already been made to the fact mentioned by Henwood
that the rich mines are situated on the granite margins. There are two
important points accounting for this peculiarity : one is that veins near
* Professor J. H. L. Vogt, " Cassiterite Veins are genetically independent of the
immediately adjacent country Rock : " " Problems in the Geology of Ore Deposits."
Mr. J. B. HUl states that the ores were possibly derived from the lower part of
the granite itself (Plutonic and other Intrusive Rocks of West Cornwall in their
Relation to the Mineral Ores : " " Trans. Roy. Geol. Soc. Corn.," vol. xii. part vii.,
1901, p. 594).
Mr. J. B. Scrivenor says : "... all wholly blue tourmaline in granite modifica-
tion has either been derived from orthoclase, or crystallised in its present state
•directly from the magma, whether fluid or vaporous" (" Quart. Journ. Geol. Soc,"
vol. lix., 1903, p. 152).
t West Kitty, Wheal Kitty, Polberro, Wheal Vor, etc.
J Dolcoath is now over 510 fathoms below surface, the deepest workings being
300 fathoms in the granite. There are several elvan dykes in the sett.
§ " Trans. Amer. Inst. Min. Eng.," vol. xxiv. : J. H. L. Vogt, " Problems in the
Geology of Ore Deposits," p. 671. Waldemar Lindgren, " Metasomatic Processes
in Fissure Veins," p. 520*
CORNWALL. 147
the granite boss are more productive than those situated distant from it ;
the other is that denudation has resulted in the removal, not only of the
superincumbent Paleeozoic sediment, but also of a great part of the top
of the granite boss, and with them a considerable portion of the most
productive parts of the ore fissures, thus lowering the surface to the rela-
tively deeper portions of the lodes (Fig. 24).
Various writers have assigned different times for the arrival of the
tin and the copper in the lodes. Mr. Hill * concludes, however, that the
ores are of " approximately identical age."
All the lodes are tin-copper, and beloug to one system of fracture,
so that there seems to be no reason for not assuming that differentiation
took place from a common solution, whereby the cassiterite was con-
centrated mainly in one place, while the more soluble copper mounted
to greater heights and was not so restricted in its occurrence.!
In the Camborne district it would be difficult to dissociate from the
same origin the ores of wolfram, arsenic, zinc, lead, and silver.
Secondary Co7icentratio?i, — It is generally admitted that secondary
concentration of copper and the chemically allied metals takes place
throutrh the agency of ordinary underground waters. The papers of
J. F. Kemp | and H. F. Bain § include masterly contributions to our
knowledge of the underground circulation of waters, while the paper of
Van Hise is full of ideas of much interest. || Mr. Kemp has already
alluded to the dryness of mines at great depths, and although I have not
the precise figures of the amount of water pumped in the past and at pre-
sent, the evidence in such mines as Dolcoath, Carn Brea, Cook's Kitchen,
East Pool, and Wheal Agar show that his observations are correct. IT
It seems that the denudation that has gone on since the lodes were
formed is the process which determined the second concentration of
sulphides. " Before the upper portion (of a lode) shares in the dis-
integration and denudation that are going on at the surface, it has
already parted with its metalliferous contents, which have gone to
enrich the lode below. Consequently, according to this view, the
enrichment of lodes must be descending at a corresponding rate with
surface denudation."** Professor Emmons has illustrated the processes
* J. B. Hill, R.N. (H.M. Geol. Survey), "Trans. Roy. Geol. Soc. Corn.," vol. xii.
part vii., 1901, p. 693.
f Professor Vogt's " Cassiterite Veins," including primary copper. Arsenic may
be included.
I J. F. Kemp, " The Igneous Rocks in the Formation of Veins : " " Trans.
Amer. Inst. Min. Eng.," vol. xxiv.
§ H. F. Bain, " Relation of Ore Deposits to the Circulation of Underground
Waters : " " Twenty-Fifth Ann. Rep. U.S. Geol. Survey," chap. iv.
lie. R. Van Hise, " Some Principles Controlling the Deposition of Ores : "
"Trans. Amer. Inst. Min. Eiig.,"vol. xxiv.
If I am informed by Ciptain Leonard Thomas that the waters in Levant mine
come from above the 60-fathom level, and the mineisquite dry at the 338-fathom level.
** J. B. Hill, R.N. (H.M. Geol. Survey), " The Plutonic and other Intrusive Rocks
of West Cornwall in their Relation to the Mineral Ores:" "Trans. Royal Geol.
Soc. Corn.," vol. xii. part vii., 1901. p. 586. See also " Secondary Enrichment of
Ore Deposits," Professor Emmons, " Trans. Amer. Inst. Min. Eng.," vols, xxii and
xxiv., p. 463.
k2
148 TIN DEPOSITS OF THE WORLD.
by which copper ores can decompose into sohible salts, migrate, and
under suitable conditions regenerate with comparative ease.* Tin, on
the other hand, and its accompanying vein constituents, are extremely
stable, and practically impossible to alter by ordinary weathering pro-
cesses. The existence of rich secondary copper ores may imply a
fissure once admitting surface waters freely. Immense quantities of
black, grey, and yellow copper ores were taken from the Basset lodes,
seven or eight in number, to the 110-fathom level, but all of them
ceased to be productive after that.t Black and yellow copper ores and
native copper were also found alongside of tin in the middle lode (which
is mainly in granite) at South Condurrovv mine, but only to the seventy-
fathom level, where the granite is rather rotten.
I Vertical distribution of the commercially valuable ores in the Cam-
borne Lodes, — The lodes with a general bearing of E. 30° N. are
parallel to the margin of the Cam Brea granite, and the information
can be generalised for each series of lodes.
The South Crofty Series of lodes includes those lodes in Wheal
Tehidy (on the east). Wheal Agar, East Pool, South Crofty, North
Crofty, East Crofty, South Roskear, and Crane (on the west),
situated along a line about half a mile north of the margin of the
granite.
The average depth at which granite was first encountered in the
principal mines in the foregoing list is about 170 fms. below tlie sur-
face of the killas. On the west it is greater, and on the east less.
The lodes are characterised by good gossans. The copper ores were
especially abundant from the higher levels (where they were oxidised)
to varying depths in the different mines, but, generally speaking, 150 fms.
below the surface marks the limit of occurrence in depth. Tin ore was
worked from 80 fms. above the surface of the granite to the deep
workings below. Wolfram was abundant (especially in East Pool)
from 10 fms. above the granite surface to 10 fms. below, but in smaller
quantities it has a wider range. Other minerals, occurring principally
in the higher levels, include ores of cobalt, zinc, and uranium. Mispickel
is a common ore.
The Dolcoath Series of lodes included those lodes in Barncoose
(on the east). Wheal Druid, southern part of East Pool sett, Carn
Brea, Tincroft, Cook's Kitchen, New Cook's Kitchen, Dolcoath,
Camborne Consols, Camborne Vean and West Stray Park, etc. (on the
west). The principal mines are situated along the margin of the Carn
* S. F. Emmons, "The Secondary Enrichment of Ore Deposits," "Trans. Amer.
Inst. Min. Eng.," vol. xxiv.
There was an instance of migration of copper in actual process at Great Con-
durrow mine, where, at the 140-fathom level, a stream of water, with copper sul-
phate in solution, issued from the lode and precipitated copper on the metal-work
in the shaft. Water, at a temperature of 102° F., was also met in North Roskear at
the 160-fathOm level, indicating energetic action.
f There was a period of poverty lasting seventeen years at Dolcoath mine before
the rich tin was discovered below the rich copper ore which had been worked out,
X D. A. MacAlister, " Summary of Progress Geological Survey," 1903.
CORNWALL. 149
Brea Granite. The main lodes first encounter the granite at about 100
to 130 fms. below the surface of the killas (on the west of Dolcoath it
is ove»220 fms. below). The main lodes all have good gossans. The
copper ores in Cook's Kitchen and Dolcoath were very rich down to
about 200 fms. below the surface, but in the former mine copper con-
tinued to occur down to 360 fms. below the surface, but was not so
valuable in depth. Tin ore in Dolcoath was especially abundant from
180 fms. below the surface to near the bottom of the mine, which is
now down to the 485 fm. level, where the lode is 42 feet wide and
contains about 25 lbs. uf black tin per ton. In Carn Brea the lodes
were very poor in tin in the deep levels, although tin occurred in
greater or less quantity right up to the surface before it was worked
out. Exceptional ores for this district were those of silver, which
occurred in the " Silver Course Lode " in Dolcoath at a comparatively
shallow level.
In the Great Condurrow Series, situated further south and con-
sequently entirely in granite, the tin and copper ores w^ere mixed,
but copper was not abundant below the 200 f m. level. Tin ore occurred
in the lodes froni the surface downwards.
The Great Flat Lode Series includes Wheal Basset (and other
mines on the east). West Basset, South Frances, Wheal Frances,
West Frances, Wheal Grenville, South Condurrow, South Tolcarne,
and several trials (on the west). On the west the Flat Lode Series is
practically wholly in granite, and lies in a valley situated between ihe
Carn Menelez Granite and its Carn Brea outlier. In going eastwards
the granite is found at a greater depth, and the Flat Lode itself
passes out of the granite into the killas and lies parallel to, and not far
removed from, the granite surface. The more or less vertical lodes
which intersect the Great Fiat Lode pass into the killas eastward.
The Flat Lode has never contained much copper, but in South
Condurrow and Wheal Basset copper has been found in small quantities
(as "native," oxidised, and sulphide ores) to 80 fms. below the surface.
Generally speaking, it is a wide lode of low grade tin ere. The more
or less vertical lodes which intersect the Great Flat Lode were mainly
copper. In Wheal Basset these lodes, eight or nine in number, con-
tain copper to a depth of 150 fms. and are poor below, although still
in killas at that depth. On the west, w^iere the vertical lodes are in
granite, they are not copper-bearing to such depths.
The Great Flat Lode. — Sir Clement Foster "^^ states that a part of
the lode left standing in Wheal Grenville is 1 to 8 feet in thickness,
and in South Condurrow the tin-bearing part is 5 or 6 feet in thick-
ness, but that the total width including the barren capel in either wall
of the lode is 12 to 20 feet. In West Basset the lode and altered
country rock at the 140 fm. level are 40 to 50 feet in thickness. R. H.
Thomas t observes that in Wheal Uny this same lode varies from
* " On the Great Flat Lode." Q. J. G. S. (1878), vol. xxxiv, p. 640.
t " Some observations on the Great Flat Lode." R. Corn. Poly. Soc. (1886),
p. 184.
150 TIN DEPOSITS OP THE WORLD.
4 to 10 feet in thickness and in one place near a cross course the lode is
72 feet wide.
The following examples of the variation in width in the different
parts of a lode are cited by Henwood.* In Tincroft Mine some parts
of the Highburrow Lode are but 3 or 4 feet wide whilst others are
30 to 40 feet. The Engine Lode at (Wheal Crofty) North Koskear
varies from IJ to 18 feet. The Main Lode in Wheal Vor varies from
3 to 30 feet. The Bor Lode in Polladras Downs varies from an inch to
4 feet. In Nangiles the lode reached a maximum width of 30 feet.
Levant Mine (St. Just). — The operations are almost entirely cou-
fined to the parts of the lodes whiv^h intersect the greenstone sill
fringing the coast. The granite plunges beneath the killas in a north-
westerly direction at an angle of 50°. Beyond the killas (a thickness
of oyer 100 fms.) the sill of greenstone underlies in the same direction
as and approximately parallel to the surface of the granite. The lodes
striking from the granite in a north-westerly direction cut across the
granite and the greenstone approximately at right angle-". Mining
operations, although at present almost entirely confined to the green-
stone " country," do not appear to have revealed its outer boundary.
The lodes are unproductive or very poor in the granite for both tin and
copper ores, but they get more productive in passing from that rock
into the killas and greenstone beyond. Although there seems no
reason for supposing that the greenstone in any way contributed in
localising the productive belt, it is worth noticing that the ore ground
seems to be persistently associated with that rock fr*»m quite near the
surface to the deep levels (338 fm. level). For a great distance the
ore ground is, practically speaking, coincident with the greenstone, but
it should be regarded as bearing a definite relation to the surface of the
granite, and the ore ground actually removed in mining operations is
seen to be roughly parallel to it.
Gurlyn Consolidated Tin Mines (^Cornwall) Ltd. — Marazon
District, — This company hold the following properties : — The Gurlyn,
Nantarras, East Trevelyn, Penberthy Croft, Enny's Wheal Virgin,
Wheal Kidney, Tindene and Retallack Tin Mines.
This important group of mines is situated in the pre-Devonian slates
of West Cornwall. In this area the sedimentary rocks present all the
characteristic phenomena of contact alteration by proximity to the
Godolphin granite mass, and petrographical examination of the rocks
in the vicinity of the mines shows them to have been affected consider-
ably by vapours emanated during the final phases of consolidation of the
granite intrusion. It is during this period that the deposits of tin-ore
were produced, and it is for this reason the occurrence of the mines in
the metamorphic area is emphasized. The fact of the occurrence of
these mines in the killas area in no way militates against the con-
tinuance of the deposits to great depths. On the contrary it is rather
an advantage than otherwise, as killas is an easier rock to break than
granite.
* Tr. Roy. Geo. Soc. Corn. (1843), vol. v., p. 240.
CORNWALL. 151
Work is being actively carried on at the Gurlyn mine, and a ten-
stamp Calif ornian mill with complete dressing plant is in course of
erection. A 8peery vanner will be employed on the treatment of the
pulverized ore. This is the first time this machine has been used in
Cornwall.
The whole series of the mines in question show evidences of a large
amount of work having been carried out in the past, and probably em-
brace the finest series of continuous ore bodies at present unworked in
Cornwall.
In the St. Just district there is a variety of schorl rock locally known
as "ramp." A common type is a druse aggregate of quartz and
granular and acicular tourmaline crystals, the texture varying froa>
compact to coarse. Formerly, in East Levant Mine, there was evidence
that at least one tin lode intersected a course of " ramp," which thus-
appears to be an older formation.
Small quantities of detrital tin ore deposits are still known to exist,,
but we can now say, as Mr. Henwood said nearly 20 years ago, that
having been wrought from remote antiquity they are now nearly, but
not quite, exhausted.
These deposits have been admirably described by various observers ;
Mr. Henwood describes them with more or Jess detail.* In all of these
the richest " tin ground " was found resting directly on the solid rock,
beneath the "shelf" or "bed rock." This was usually covered with
several alternating layers of peat or vegetable-mould, sand, and gravel.
Sometimes an upper and poorer layer of tin ground occurred, resting in
a " false-shelf " not far beneath the surface ; the components of this
upper layer being, as Mr. Henwood observes, less rounded than those
of the true tin ground. He also remarks that the components of the
tin ground generally are more rounded in proportion to their distance
frorti their elevated source, and furthermore that the more elevated tin
grounds resemble in mineral character the rocks upon which they rest,
while those nearer the mouths of the valleys have no resemblance.
The detrital tin ore of the West of England occurs as crystals,
pebbles, sub-angular masses, and water-worn grains of cassiterite,
sometimes associated with similar fragments of iron pyrites and other
" heavy " metallic minerals, and occasionally even with small nuggets
of gold.t The cassiterite is sometimes attached to fragments of granite
or slate, or to pieces of quartz, felspar, or other veinstone, but more
commonly it is free from such attachments. In any case, it forma
but a very small proportion of the " tin ground," rarely exceeding 5 per
cent, of its mass, and often not so much as one-tenth of 1 per cent.
It would be impossible to describe in detail all the mines in Corn-
wall. The chief districts where tin mining is now carried on are
Camborne, Redruth, St. Ives, St. Agnes, St. Austell, and Levant.
With regard to the future of tin mining in Cornwall naturally
opinions differ. The author has come to the conclusion, after exami-
nation of several of the old mines in Cornwall, that undoubtedly there
* J. H. Collins, "Origin and Development of Ore Deposits."
t See " Jouf'. Roy. Inst. Corn.," 1873.
152
TIN DEPOSITS OP THE WORLD.
aire still good openings for the successful employment of capital.
Modern methods of mining and tin dressing, together with the high price
ruling for tin, would make for success, and it is by more extensive
exploration that the old mines will pay. There have in the past been
several periods of depression in Cornwall when the price of tin ruled
very low and fresh capital was unobtainable. It was during these
periods that some old mines were forced to close down which would
return handsome profits to-day if properly equipped.
* Tin Statistics for Cornwall, 1906.
Com-
1
AversLge Price
1906.
puted
TnnR
^^^J^S^V^'^<^^ Values,
per ton. |
ot Metallic Tin
per Ton on day
xutio.
1
f 8.
d.
of Ticketing.
£ s. d. '
£
s. d.
January
1 ...
183i j 94 3 2 1 17,772 5
195
15
15 ...
246J
97 12 6 : 24,066 10
170
29 ...
202i
96 9 2 1 19,532 17
6
167
February
rl2 ...
237
96 15 10 : 22,939 18
9
166
10
26 ...
207i
97 16 1 20,270 1
10
165
2 6
March
12 ...
252 : 97 6 7 24,527 6
3
165
26 ...
216i 99 3 3 21,494 2
6
167
10
April
9 ...
232i 101 11 7
23,617 3
9
171
10
23 ...
204 ! 104 11
21,327 13
9
176
May
7 ...
255 1 113 7 6
28,906 15
191
15
21 ...
213i 107 11 9
22,943 2
6
185
June
6 ...
254 105 12 7
26,829 16
3
179
18 ...
202i
104 7 4
21,108
177
July
2 ...
254f
102 14
26,163 7
6
177
16 ...
210
97 13 9 20,514 8
9
168
10
30 ...
232i
98 15 5
22,939 7
6
172
10
August
13 ...
202i
104 9 10
21,133 12
6
183
5
27 ...
241
104 19 9 25,302 17
6
184
Sept.
10 ...
185
105 11 4
19,530
184
24 ...
228i
106 8
24,312 11
3 185
5
Oct.
8 ...
191i 1 113 5 10
21,695 6
3 195
10
22 ...
241i
113 19 8
27,528 7
6
197
10
Nov.
5 ...
1914
114 5 11
21,888 1
3
197
5
19 ...
242
113 2 1
27,381
195
12 6
Dec.
3 ...
1874
114 4
21,412 15
197
5
17 ...
258f
113 10 5 29,373 1
10
197
5
31 ...
195
114 4 1 22,270 1
3
193
12 6
Tot
al
B 1905 ver
'5,973 J
1 ~
626,780 11
2
—
Sine
y considerable intereg
\t has been
taken in reopening
the Cornish mines.
several
large Limited
Liability Compt
mies have been
* "Mining Journal," London, 12ih January, 1906.
CORNWALL. 153
floated, the old cost-book methods having fallen into disuse. In
several instances sufficient capital has been subscribed to thoroughly-
test the lodes at a depth. The machinery being installed is of a most
up-to-date description, and upon-the result of these ventures the future
of tin mining in Cornwall will largely depend.
Thirty companies were registered to reopen and work the Cornish
mines in 1906 having a total nominal capital of £1,184,700.
( 154 )
CHAPTER XIII.
TIN DEPOSITS OF NORTHERN NIGERIA, TRANSVAAL,
SWAZIELAND, CONGO FREE STATE, JAPAN,
GREENLAND, FINLAND, CHINA, KOREA, AND
SIBERIA.
Tin Deposits of Northern Nigeria.*
The occurrence of tin in Northern Nigeria has been known for
many years past by the presence of quantities of small faggots of very
pure metal in the native markets, which occasionally found its way
down to the coast. Until three years ago, when the territory was trans-
ferred from the Royal Chartered Niger Company to the Colonial
Government, the country away from the valley of the Niger and
Benue was practically unknown, but as soon as the Goverument had
satisfied themselves as to the safety of travelling in the territories the
Niger Company despatched an expedition for the purpose of a geologi-
cal examination of the country east of the Niger, and if possible to
locate the tin -bearing areas.
The tin was eventually traced to the Province of Bauchi, some
600 miles to the north-east of Lokoja, the then headquarters of the
Government, situated at the confluence of the Niger and Benue rivers.
Further prospecting located the stanniferous area to the outliers of
the Gura Mountains, a small range known as the Naraguta and Shere
Hills, in the Badiko district of that province. The tin was found as
coarse and fine-grained alluvial stream tin in the beds and banks of the
River " Gimpy " or Kogin-Delume (this translated from Hausa is
Kogin-River and Delume-Tin).
The geology of the area is composed of granites, igneous iutrusions
of diabase and porphyry forming the prominent peaks of the hill
range. Near the river a coarse grey gneiss forms a contact with the
granite, both of which rocks are traversed by lenticles and gash veins
* This account was written for the author by M'. R. C. Nicolaus, December,
1904.
NORTHERN NIGERIA, TRANSVAAL, SWAZIELAND, ETC. 156
of quartz, and several small igneous dykes cross diagonally the general
strike of country, which is north-east and dips west.
The stanniferous area has now been narrowed down to approxi-
mately 25 square miles, and although the stream tin has so far only
been prospected near the river there is abundant evidence to show that
the source of the tin supply comes from a stock work formation in the
granite at the slopes and at the base of the foot-hills.
A somewhat remHrkable feature of this deposit is that a considerable
quantity of metallic tin has been discovered under the river banks,
during prospecting operations. It is found in small grains and nodules
about the size of a bean, and its surface very thinly coated with a film
of oxide, the metal being very pure, containing only a trace of iron ; it
is very ductile and emits on .crushing the peculiar tin cry. Its mode
of occurrence in the gravels and associated with coarse grains of stream
tin at a depth of some 15 feet under the surface does not allow its
genesis being determinable, but it can without a doubt be put down as
" native tin," a mineral up to the present of very rare occurrence.
The stream tin contained in the gravels is generally coarse, the
average product so far obtained by tests being 35*66 lbs. per ton of
alluvial. The procedure of the uative in securing this black tin is as
follows : —
The washers (Hausa men and women), usually working in gangs
of three or four, wade into the river, tributary creeks, and gullies,
generally at or near some shallow rapids, and loosen the gravel under
water with a short hoe-like implement and scoop it into large calabashes
about 18 inches to 24 inches in diameter. As soon as sufficient gravel
is collected (about 30 lbs.) it is washed and the resulting rough con-
centrates placed in a smaller calabash, 6 inches to 8 inches in diameter,
and thoroughly cleaned (nearly all the fine tin being lost), the resulting
black tin, containing 60 per cent, to 65 per cent, metal, is sun dried
and packed in bags and skins for transport to the smelting furnaces,
18 miles distant.
A gang of four will average in an ordinary day's work 80 lbs. to
1 cwt. of clean black tin.
The local market value of this black tin works out at £15 155. per
ton.
The black tin is usually smelted in various parcels on a royalty
basis exclusively by members of a family who hold the process a great
secret. Only three smelting furnaces are in use, and are only capable
of turning out about 2 cwt. a day each. They are built of well-puddled
clay, and are 3 feet 6 inches diameter, having at the back four tuyere
holes conducting the blast from primitive sheepskin bellows to the
hearth. The tin is reduced by charcoal only, and runs through a
channel 2 feet 6 inches long and 4 inches broad into a catch-pot, from
where it is ladled by small gourds or calabashes and poured.
The cast tin takes the form of 12-inch long strings of about ^ inch
diameter, which are produced by pouring the molten metal on to an
.18-inch high semi-circular bank of clay which is perforated bv dry
guinea-corn halms.
156 TIN DEPOSITS OF THE WORLD.
The aaaljsis of the matal is as follows : —
Analysis of tin bar received :
Tin 99-400
Iron -520
Lead - - - - - - - '015
Loss -^ '065
100-000
Very little tin is lost in the prooess, as all slags are carefully
y collected, re-crnshed, washed, and concentrated, and the product added
to the next smelt.
Tin Deposits in the Transvaal.
Some tin lodes and alluvial have been discovered in the No. 373 Dis-
trict of Pretoria. Harry D. Griffiths, in a report on the tin deposits,
writes as follows : —
^^Bushveld Tin Mines Ltd.
" Geology, — The rocks encountered on your property are almost
exclusively red granite. The granite is of a very coarse variety, with
a great development of orthoclastic felspar, and occasional presence of
tremolite or actinolite. Plagioclastic felspar is either rare or totally
absent. The granite forms practically a boss, running north and south,
and limited to the east by a wide volcanic intrusion running north and
south along the eastern boundary of the property, and covered by a
great thickness of sand and detritus to the west. Grey granite occurs
in sporadic patches on Enkeldoorn. To the north volcanic intrusions
are again in evidence, and to the south and south-west secondary
measures are obtained. In the centre of the boss the granite contains
a system of lodes or fissure veins running slightly east of north, in
the vicinity of which the granite is of a finer structure, although its
components appear the same. In addition to the main system of lodes,
several cross lodes are encountered on Enkeldoorn and Zustershoek.
" The Lodes. — The lodes consist of a series of almost parallel
fissure veins, whose outcrops can be followed for considerable distances.
These are most conspicuous on Enkeldoorn, but can be found again on
Rietfontein, and can be followed almost continuously into Zustershoek.
The strike appears most regular, and no dislocations are apparent. The
cross lodes, which bear similar characters, do not appear to have dis-
located the strike of the lodes, or vice versa, and it would appear,
therefore, that they are contemporaneous with one another.
"The lodes have a slight dip to the east, the maximum inclination
noted being 82 degrees from the horizontal.
" One of the lodes striking north and south has been opened out by
means of trenching for a considerable distance ; this has bfcn called so
far the ' Main Lode,' and for the sake of simplicity this denomination
TIN DEPOSITS IN THE TRANSVAAL. 157
will bo retained. It shows the walls of the lode to be well defined with
fine grained granite hanging and footwall. The matrix of the lode is
composed of quartz and orthoclase, fine-grained and generally of a light
colour, with rare flakes of mica (mnscovite). Its structure is pegma-
titic, and hence the matrix has generally been called pegmatite, although,
owing to the fine-grained structure in depth, it should be more properly
denominated as aplite. The ore body shows floors of horizontal joints
at close intervals without signs of lateral displacement of the walls ;
and the enclosing granite shows joints mostly at right angles to the
course of the lode. Disseminated in the mass are found pyrites and
cassiteritQ. The pyrites, as shown by analysis, contain a small amount
of arsenical pyrites. The cassiterire is ]jretty pure, but encloses a
small proportion of pyrites. So far the presence of titauiferous iron
aud of tungstate of iron (wolfram) has not been detected, although they
may make their appearance in depth. The presence of these in the
ore would render the roasting of the cassiterite necessary before smelt-
ing. The presence of wolfram in appreciable quantities would probably
be an additional source of revenue, as its price has risen considerably
of late, aud its special extraction would not add much to the cost of
treatment. The ' Main Lode,' so far as exposed in numerous trenches,
is generally well defined close to the surface, and shows a total thick-
ness of as much as 1 2 feet. In some trenches the lode is split up into
stringers separated by fine grained country rock, but having a distinct
tendency to unite in deptli. In places the outcrop of this lode shows
a width of over 20 feet. The trenches have exposed the reef over
one mile, and three small shafts have attained a depth of 50 feet.
Wherever this lode has been touched it has been found tin-bearing, and
in some instances of great richness.
" Cross Lodes, — To the south of the camp on Enkeldoorn two well-
defined cross lodes are encountered, the first being some 460 yards south
of the spruit, and the second some 250 yards further. The first one
shows a powerful outcrop of a width of about 12 feet, and it strikes
28 degrees S. of E. magnetic. Where it crosses the main lode and
first east lode the junction is well exposed, and there is no dislocation
apparent. This lode is again obtained due east of the camp in the
road, where it is apparently over 4 feet in thickness. Continuing its
course to the east, it finally abuts against the large elvan dyke, which
cuts it off. The second cross lode has also a regular strike, but its
outcrop does not show so prominently as the first.
" In the southern portion of Zustershoek occasional outcrops towards
the spruit give evidence of the occurrence of another cross lode.
North of the camp, and 6,000 feet south of the Enkeldoorn northern
boundary, two outcrops of cross lodes occur within 100 yards of each
other. The outcrops are very wide where they peep out from under
the overlying sub-soil.
" As far as is evidenced, the lodes appear to be true fissure veins, and
their permanence in depth assured. The gossan or iron capping which
is almost invariably found in metalliferous lodes is well in evidence
with each of the lodes.
158 TIN DEPOSITS OF 'THE WORLD.
" The number of lodes and cross-lodes as above stated is as far as
can be ascertaiued for the present, and cannot be taken as representing
everything in the shape of lodes that may occur on the property.
Where the bed rock is exposed on high ground the outcrops can be
well followed, but a large portion is covered by surface drift, which
will necessitate extensive prospecting.
" The presence of tin in most of the samples taken from the capping
of lodes and cross-lodes is a most encouraging feature.
"TAe East Elvan, — Following as near as possible the strike of the
main lode, and east of the camp beyond the most easterly cross-lode,
a huge elvan dyke occurs. Its thickness to the west has not been
ascertaiued. The strike can be followed almost all along the eastern
boundary of Eukeldoorn, and on Zustershoek it is again well in evidence
at the most easterly beacon. The dyke, judging from surface samples,
appears to be composed of a confused mass of felspathic rock and
serpentine. The felspar rock shows orthoclase blended with actiuolite,
both being coarse in texture, and is probably derived from the breaking
up of the granite with alteration of its constituents. Quartz appears
in rounded grains, and is most abundant in the vicinity of the hematite
body, where the rock strongly resembles quartz porphyry. Serpentine
is abundant, but whether it constitutes the bulk of the elvan, my obser-
vations have not yet established. It is of a dark green colour, with
enclosures of garnet rock and specks of muscovite and pyrites. Occa-
sional enclosures of titaniferous iron aie encountered, as well as altered
felspar and occasional quartz stringers. The rocks of the elvan are
apparently greatly mixed, and will require a more lengthened study
than I have been so far able to undertake. The fact of the cross-lodes
stopping short against the elvan mould shows the latter to be of
younger origin than tbe lodes. The elvan contains well away from its
western edge a body of hematite. This has been opened out in a
shallow shaft on Enkeldoorn and shows a thickness of 12 feet. Both
walls of the body are well distinct, and the dip is 80 degrees to the
east. The hematite is again exposed on Zustershoek in a trench.
At this point the width has not been ascertained, and being mixed
with a quantity of quartzose matter it is not so rich as in the first
shaft.
" It is probable that tbe dip of the hematite body corresponds to that
of the elvan, and in that case, so far as your properties are concerned,
the elvan would not have any detrimental effect in cutting off the lodes
in the dip.
^'Alluvial Tin, — The westeru portion of Enkeldoorn is composed of
low-lying and flat country, and covered over by a great thickness of
detritus. This extends on the gentle slope of the rise to the outcrops
of the lodes. On the slope the thickness of the drift averages 3 feet,
whereas on the flats I feel certain that a very much greater thickness
will be obtained. Samples of the drift gave in every instance the
presence of cassiterite, and should prove payable if worked on a large
scale."
TIN DEPOSITS OP THE TRANSVAAL. 159
In the engineer's report of 31 St July, 1905, a total of 1,341 feet
has been snnk and driven in this property with encouraging results.
Tin Deposits of Cape Colony.
Kuils River Tin Mines. — They are 12^ miles from Cape Town
and cover an area of 5,037 miles. The country rock consists of granite
which* belongs to Cape system. The hills are traversed in a north and
south direction by bands of greisen, with closely associated quartz lodes
dipping to the east.
The granite is grey passing into a syenite. The greisen is charac-
terised by a large proportion of mica and the quartz constituents are
mostly fine grained. The quartz is generally white and compact,
showing occasional patches of mica, and containing minerals in the
shape of cassiterite and wolfram.
Near the surface the lodes dip to east at an angle varying from
25 degrees to 35 degrees from the horizontal.
As far as ascertained the chief source of the minerals is the quartz -
reef, although the greisen shows mineralization. The decomposed
granite intervening between the band of greisen and quartz appears to
be impregnated in the vicinity.
Alluvial Tin. — This was first discovered in the creek in Langver-
wacht. The chief ascertained source of the alluvial tin is a loose
breccia of angular fragments of lode quartz cemented together by
kaolin! sed matter containing cassiterite in angular and sub-angular
pieces as large as 3 in. cubes.
This breccia rests on more or less impure kaolin, the result of the
decomposition of the country rock ; this decomposition is very extensive.
The breccia in parts carries considerable quantities of cassiterite.
Mr. H. D. Griffiths, in his report in June, 1905, stated that : —
"I estimate therefore the total yield of the alluvial on the pro-
perties cannot be less than 25,000 tons of cassiterite having a gross
value of £2,250,000."
SWAZIELAND TiN FlELD.
This field was discovered by Mr. Ryan in 1889.
The geological features of the tin district are briefly described as
follows : — *
Granite bosses flanked by metamorphic rock intersected by elvan
dykes, diorite and rhyolite. The tones of quartz and hornblende-schist
and steatite may be observed striking N.N.W. by S.S.E. and dipping
slightly west, being apparently of a much older formation ihan the
" Golden Beet " resting uncomformably a few miles north.
* Chemical and Metallurgical Society of South Africa.
160 TIN DEPOSITS OF THE WORLD.
The following is the order in which the intrusive rocks occur : —
1st. Intrusive granite which has undoubtedly tilted the schists.
2nd. Elvan dykes striking N. and S. and dipping at an angle
of 30 degrees -west.
3rd. Diorite dykes intersecting the formations in all directions.
4th. Rhyolite cutting through the formations in a N.E. direc-
tion. This is undoubtedly contemporaneous w^th the
Lebombo upheaval.
Elvan dykes vary in width from a few inches to many feet, and are
composed of felspar, quartz, mica, and hornblende, in which crystals of
cassiterite, garnet, monazite and tourmaline are contained. Molybde-
nite and corundum are also found in the schist which the elvan dykes
have cut.
Deposits, — " The Stream Tin " in alluvial deposits originates from
the erosion of the elvan dykes before mentioned, and is deposited in
three beds as follows : —
1. Oldest deposits yielding J per cent. tin.
2. Yielding \ per cent, to 1 per cent, of tin.
3. Yielding } per cent, of tin.
The average thickness of these beds is 4J feet through; the Lower
Embabaan and Usutu Rivers now being prospected contain beds of
considerable thickness.
The supply of labour is good, and the water supply from the Little
Usutu River and the Babaan River large and unfailing.
Assay value of the tin ore is 60 per cent, of metallic tin for about
10 per cent, of the quantity raised, and 72 per cent, for the balance.
The chief raining camp is at Embabaan about 5,000 feet, and the
climate is considered very healthy.
Tin Deposits. — Congo Free State.
Tin has been found both in the alluvial drift and in ledges on the
Tanganyika Concessions in the Congo Free State, about latitude
10° 20^, south longitude 25° 13' each, and found at intervals for a
distance of 60 miles north-west along the valley of the Lualaba
River.
The tin ore discovered all lies north of the southern boundary of
the granite belt, which extends through the country in direction about
E. 15° north, which boundary is in latitude and longitude above men-
tioned at that point.
The most important of the tin discoveries so far made is the
Busanga Tin Mine, situated at latitude 10° 12' and longitude 25° 13'
east, north of the Lufupa and west of the Lualaba, the centre of this
property being 1,200 yards N.W. of the junction of these two rivers.
TIN DEPOSITS OF THE CONGO FREE STATE. 161
* Busanga Ridge, — This ridge extends in a N.N.E. direction
parallel with the Lualaba River. It is cut by several watercourses,
which are dry except daring the rainy season.
At its southern end the height of the. ridge is 180 feet about the
Lufupa, and distant about 900 yards from that river. The ridge at the
northern end of the cassiterite area is 270 feet in height above the
Lualaba and distant 1,060 yards west of that river, with slope down
to the river. The surface of the ridge is covered with loose ground
composed of schist, gravel and quartz fragments.
The cassiterite is distributed through this loose ground from the
surface over about nine-tenths of the area down to the depth of 7 feet
in places, but in one -tenth of the area the cassiterite stratum is covered
by a clayey wash to a depth of from 6 inches to 17 feet.
Quartz Reefs, — Twenty-two cuttings from 6 to 10 feet in depth
have exposed quartz reefs, widths of from 1 to 25 feet. These reefs
stand nearly vertical, with strike generally parallel to that of the ridge,
having good walls. In all of these reefs some cassiterite is found,
mostly in a few inches of the quartz near the walls, but in a few
instances it is found diffused through the quartz of the reef to some
extent, but the quartz reefs so far exposed have not shown a percentage
of cassiterite which will pay to mine for the ore. The great body in
the aggregate of cassiterite contained in the gravel of the surface of the
ridge has undoubtedly come from the outcrops of quartz reefs which
have become disintegrated by long exposure to the weather, and the
quartz fragments now form a considerable portion of the bed of gravel
which covers the surface of the ridge and conceals the reefs from which
the cassiterite and quartz were denuded.
The cassiterite found in the gravel of the ridge is in the same form
as seen in the quartz reefs which have been exposed. The stream tin
found in the watercourses leading from the ridge shows signs of having
travelled; the further away from the cassiterite areas the more rounded
are the rolled fragments of tinstone.
The Kasonso Tin Mines are situated in the Kasonso Hills, Congo,
Africa, and consist of ten contiguous mining locations which conjointly
form a property 12 miles in length with widths of 4 J miles for a dis-
tance of 5 miles of the south-west portion, and 3J miles for the remain-
ing 7 miles of the north-east portion of the property, forming an area
of 45f square miles of 29,280 acres. The centre of the property is
about latitude 9 degrees and 24 minutes south, and longitude 25 degrees
and 48 minutes east.
The Kasonso Hills are a distinct range of rolling hills extending
north-east and south-west 18 miles in length and 4 miles in width,
rising at the highest point to 900 feet above the level of the surround-
ing country and 2,900 feet above sea level. The country rock of the
hills is sandstone, formation regular, the sandstone reef running with
the strike of the hills. Granite outcrops near the base of the south-
east line of the hills, near the centre of the south-eastern line of the
mining property.
* Tanganyika Concessions Report, July, 1906.
162 TIN DEPOSITS OF THE WORLD.
Lodes. — The tin lodes consist of a series of quartz vein running, so
far as can be observed, from uncovered croppings regularly with the
sandstone reefs. The lodes can be followed almost the entire length of
the property by the permanent quartz outcrop, or by quartz drifts
covering the surface, the disintegration of the reefs. Black tourmaline
and tourmaline in fine crystals, sandstones more or less altered and
schistose, and mica schist rocks and boulders are to be found scattered
over the surface with the quartz drift along the line of the tin bearing
lodes.
The outcrops of the quartz lodes are mostly covered by the drift,
and no sinking has been done upon the lodes to determine any of their
extents or values, but in trenching across the reefs and sinking pro-
specting holes to find the depth and value of the alluvial ground, the
lodes have been cut in many places for from 5 to 10 feet below the
surface, showing the existence of parallel lodes and their continuity for
several hundred feet from 2 to 4 feet in width, and giving evidence of
permanency in depth. In most places where cut by this prospecting
work the solid reefs have shown considerable cassiterite, and the drift
from all the trenches and holes sunk adjacent to any of the lodes
average especially well in cassiterite when panned.
At the Kasonso Tin Mines the total average over 12,950 yards
prospected yielded : —
Cubic Yards. Average Value Amount of
per Cubic Yard. Tin Ore.
1,132,962 28-77 lbs. of tin 14-555 tons
Water Facilities. — Falls. — The Busanga Tin Mine is very advan-
tageously situated as to water privileges for power, sluicing, and all
mining purposes, being only a few hundred yards from the Lualaba and
Lufupa, two large streams. These rivers form the eastern and southern
boundaries of the property.
There has not been sufficient development work done to ascertain
if this new-discovered Tin Field is going to bo a large and continuous
tin producer. But this tin deposit taken in conjunction with the tin
deposits of North Nigeria point to the fact that Africa may some day
become an important factor in the tin production of the world.
Tin Deposits op Japan.*
This country is also a small producer of tin ; the bulk of it is pro-
duced by vein mining, the Taniyama Mine, in the province of Satsuma,
being the chief producer, to the extent of about one-half of the total
output of lode tin. The ore is contained there in veins running east
and west, and traversing a porphyritic rock, probably rhyolite. These
veins vary considerably in width and are composed chiefly of quartz
and iron pyrites, in which occasionally bunches of tin ore are met with ;
the total production not exceeding ten tons.
* Journ. Geo. Society of London.
TIN DEPOSITS OF JAPAN, GREENLAND, FINLAND, ETC. 163
In the province of Bungo numerous eroded cavities filled with
stanniferous gravel containing from 0'3 to O'o per cent, of tin. are found
in crystalline limestone.
A little alluvial tinstone appears to be got irregularly in the
province of Mino.
The tin production of Japan used apparently to be more important
than it is at present. The average output for the last 10 years is about
12 tons a year.
Tin Deposits of Greenland.
Tin Ore Veins at Arksut, Greenland. — *" The area over which the
tin veins occur is 1,500 feet in length by 80 feet in breadth, running
E. and W., others N.E. and S.W. The tin occurs disseminated in
crystals through the rocks and accompanying the finer grained galena
and tantalite. The gangue here is felspar, quartz, sparry iron and
fluorspar. The veins are small and belong to the underlying granite,
which appears at the surface in veins, and which is probably at not
great depth below, since the tin veins penetrake into the overlying
gneiss, which dips to the south and under the outcrop of granite loses
itself.
" It is highly probable that the cryolite forms a bed between the
gneiss and the granite, and partly enclosed in the gneiss. This tin
district differs from all others known, being associated with the
cryolite, whilst tantalite seems to have taken the place of wolfram."
It is of no commercial importance.
Tin Deposits op Finland.
+ Tin ore occurs at Pitkaranta on the north shore of Lake Ladoga.
Here, too, the geological structure of the country is seen to consist of
crystalline sedimentary rocks, traversed by granite. Some of the altered
stratified rocks are impregnated in places with tinstone, and are the
source of a small production of this metal.
China.
" Tin is known to be produced in the Empire of China, but nothing
definite is known as to its localities or mode of occurrence ; it is, how-
ever, fairly safe to assume," says Professor Henry Louis (in "The
Production of Tin " published by the Mining Journal) " that it is got
from alluvial deposits. In Southern China it is known to occur both
in alluvial deposits and disseminated in granite in the neighbourhood of
Kotchion, in the district of Moungtsi. This place is the centre of an
active tin-producing industry, work being carried out on a large scale ;
the district is said to produce about 3,000 tons of tin annually. The
* J. W. Tavlor. XV. Jour. Geo. Soc.
t " The Production of Tin," Louis.
L 2
164 . a'XN DEPOSITS OF THE WORLD.
total tin output of China has been variously guessed at 10,000 to
20,000 tons per annum, though, whatever it be, it is evidently insuffi-<
cient for the needs of the country, as China imports tin from Siam, the
Siamese-Malayan States, the Straits Settlements, aud the Netherlands
East Indies. It is also quite possible that the neighbouring Shan
States, Cochin-China, etc., may send some tin into the Chinese Empire,
as the former are said to produce some. It will be remembered that
the Chinese have from time immemorial been in the habit of employing
bronze largely, this body being an alloy of copper and tin."
"^ China* s Tin Exports in 1905.
Mr. Wilkinson, British Consul-General at Mengtzu, reports : — The
past year (1905) is the record year for tin. Although owing to the
enormous increase in the cost of labour, due to the requirements of
the railway, the mine-owners of Kochiu had to reduce their staff by
one-half, still the mines and the town had completely recovered from
the damage done them in the rebellion of 1903. The result was an
export of 74,972 pikuls (89,252 cwts.), valued at £514,034, or 72 per
cent, of the total exports. The whole of the tin is shipped to Hong
Kong in half slabs measuring 22 inches in length by 9 to 10 inches in
breadth and f to 1 inch in thickness. Each half slab (the original
" pig '* is always cut into two, chiefly for convenience of mule carriage,
but also to show the quality) weighs 55 catties (73 lbs.). Its market
value in Mengtzu before payment of export duty is, roughly, £6 per
pikul of 133 lbs. The trade is entirely in the hands of the Chinese,
who would be very jealous of any interference.
Mr. Consul Carlisle, in his report for 1905, says : — The export of
tin is an incident of the transit trade. The tin comes from the mines
of Ko Tiu, near Mengtse, in Southern Yunnan. These mines are
exploited by Chinese who bring the tin into Mengtse, whence it is sent
down to Manhao on the Red River and thence through Tonkin to Hong
Kong. The total amount of the export during the year was 4,578 tons,
valued at £553,915, and of this value only £2,231 refers to Indo-
Chinese tin (mostly ore), the bulk of the rest being the Yunnanese
product. £526,828 worth of tin came in during the year. This was,
of course, the same tin in transit that here appears as an export.
Korea.
Tin is said to be mined in the province of Chulla, at Hainan,
Koangchow, and Chyeichow ; it does not appear that the production
attains dimensions of any importance.
Siberia.
Tin has long been known to exist in the district of Nerchinsk
(Transbaikal), chiefly in the valley of the River Onon, an affluent of
the Amur, where deposits of tinstone are known over an extent of above
* "Mining Journal," Sep. 15, 1906.
TIN DEPOSITS OF ^HINA, KOREA AND SIBERIA. 165
70 miles. This resrion is rich in gold placers, and in washing these
tinstone was found along with the gold ; this discovery led to investi-
gations which resulted in finding the metal in primary deposits in the
year 1811. Tin had, however, been worked long before this by the
native inhabitants. Here again the country consists of schists, up-
heaved and traversed by granites, Jt>pjbh the stratified and the eruptive
rocks being penetrated by a network of veins and veinlets of quartz,
carrying, together with the tin ore, the minerals which elsewhere also
characterise similar deposits. This region is remote and almost un-
civilised, and it appears that work was conducted very crudely and
unsystematically, mining in the true sense having scarcely been
attempted. It is said that old statistics show that the crude ore raised
contained as much as 6J per cent, of metal. Nevertheless, the industry
was never really successful, a fact to which the inaccessibility of the
district, no doubt, contributed largely. No work seems to have been
done there since 1852, and no statistics as to the amount of tin pro-
duced are available. In view of the fact that the Trans-Siberian
Railway passes not far from this district, it is now proposed to recom-
mence operations, and if its extent and richness are as considerable as
they are reported to be, this may one day become an important centre
of tin production.
( 1^6 )
CHAPTEK XIV.
TIN DEPOSITS OF CENTRAL EUROPE, SPAIN, PORTUGAL^
FRANCE, ITALY, SCOTLAND, IRELAND, MEXICO,
UNITED STATES OF AMERICA, AND ALASKA.
Tin Deposits of Central Europe.
Tin Mining in Central Europe was an important industry for many
years. Tin was first worked in the Altenberg district in 1459 ; the
output was not over 300 tons for many years, and this has gradually
dwindled away to comparatively nothing. The geological features are
interesting. The rocks round Altenberg which contain the large tin
ore deposits are mostly a greyish coloured porphyry, gradually merg-
ing into a form of greisen ; a large mass consisting of chiefly quartz
and mica over 1,200 feet in length and 800 in width contained the tin
ore. The ore is disseminated through the mass in exceedingly small
particles ; it is locally known as z witter, it has a dark grey or greenish
colour, and sometimes almost black. It is of a remarkably fine texture,
and is composed essentially of quartz with chlorite or lithia-mica,
spacular iron, wolfram, mispickel and cassiterite ; the quartz, which is in
an amorphous condition, is plainly distinguishable. This rock differs
from an ordinary greisen, as it contains chlorite and specular iron.
Over the whole body small fissures about 8 inches in width occur, and
this formation is now generally termed a stockwork. The rock mass
surrounding this formation is a porphyritic granite ; it is finely grained,
and carries a quantity of pink felspar.
The stanniferous strings or veins of quartz that occur are merely
extensions of those traversing the formation on either side. Van
Cotta, who has written extensively on the geology of this district, con-
siders that the " zwitter " is merely an altered form of what was once
a granite, similar to that at present next it, which became impregnated
with solutions of silica and tin in combination with other elements.
* The stanniferous deposits of Gottesberg and Brunndobra, near
Klingenthal. A few of the widespread ancient workings, abandoned
for many generations, have been lately made accessible again, and thus
a scientific investigation of the deposits has become possible. They
are evidently associated with the contact-metamorphic zone which
marks the junction of the intrusive, coarsely crystalline tourmaline-
granites with the older phyllites, quartz-schists and hornblende-schists.
In the Gottesberg district, the ore-occurrences consist partly of
small crystals of cassiterite impregnating grey quartz, and partly of
* "Zur Kenntniss erzgebirgischer Zinnerzlagerstatten. By O. Mann. Ab-
handlunger der naturwissenschaftlichen Gesellscbaft ' Isis ' in Dresden, 1904, part ii,
pages 61-73."
TIN DEPOSITS OP CENTRAL EUROPE. 167
tin-ore in a microscopically fine state of division, associated with fairly
large grains and nodules of pyrites and arsenical pyrites. In following
up a deposit of the latter kind, it is found that the sulphidic oreS
gradually assume the predominance, to the ultimately complete exclu-
sion of the tinstone. Most of the minerals that one is accustomed to
associate with stanniferous deposits, such as topaz, fluorspar, molyb-
denite, etc., are here conspicuous by their absence. Veins of chert,
bearing red haematite, are associated with the tinstone-bearing veins, of
are seen to cut across them.
In the Brunndobra district especially do the veins occur in the
contact-metamorphosed slates : the pitch is generally steep, and the
strike all but universally northerly or north-westerly. The main masd '
of the veins consists of quartz and tourmaline, the latter exhibiting
certain crystallographic characters which are reminiscent of the analog-
ous mineral from the Mount-Bischoff tin-ore deposits in Tasmania.
The tinstone seems to be concentrated by preference in those parts of
the veins which are richest in tourmaline. Under the microscope the
cassiterite-crystals are remarkable for their concentric zonal structure^
as many as ten light and dark bands alternating in some cases.
Needles of tourmaline are seen to pierce them, and in some instances
the cassiterite presents the appearance of having been " gutted," so to
say, and then " restuffed " with tourmaline ; but in no case is a cassi-
terite-crystal embedded or included in the tourmaline. Irregular masses
of red haematite are of common occurrence in the gangue. The hsema-
tite-veins proper, of later date than the cassiterite-veins, repeatedly cut
across the latter. The stanniferous veins, being only from 4 to 12 inchee^
thick, would hardly have given rise to mining operations of any con-
siderable extent, had it not been for the " impregnation-zone " extending^
on either side for about 20 inches into the metamorphosed country -rock.
In some cases, the area of impregnation was immensely extended. It
is often very difficult to determine exactly where the vein ends and the
country-rock begins. The stanniferous veins are supposed to have
been formed at a time when the granite-intrusion had already begun to
solidify superficially, and simultaneously with the silicification of the
neighbouring rocks. They are not, as at Mount-Bischoff in Tasmania,
genetically associated with the advent of the topaz (which was a later
comer than the cassiterite at Brunndobra) ; while on the other hand,
those Tasmanian tin-ores do not actually occur in tourmaline-rock as do
these Saxon ores. In outward appearance, the close resemblance between
the Mount-Bischoff and the Erzgebirge deposits is very remarkable.
Arthur G. Charleton, in his book of ' Tin Mining " (page 9), gives
the following account of mining operations at Altenberg : —
" The method in operation in these mines is the so-called ' Stock-
werks-hau,' but it can only be employed in those parts of the deposit
where the zwitter is impregnated with cassiterite in sufficient quantity,
or a network of small veins bunch together ; for it should be explained
that the mere presence of cassiterite does not alone constitute a stock-
work — Germ. Stock werk — as the term is applied only to those centres
of enrichment where the rock, though comparatively poor, appears to
168
TIN DEPOSITS OP THE WORLD.
be rich enough to be mined at a profit. Stoekwerks-bau would indeed
never be followed unless considerable portions of the rock were barren,
and the value of the pay-rock comparatively so small and variable
that large quantities must be got out to make it pay ; and, from
circumstances outside of the miner's control, no regular plan of
working can be maintained underground.
'*In mining by this system at the present time, drifts are driven
from the Romer shaft at every 63 feet in depth with the aid of
explosives ; and as soon as the deposit is reached, cross-cuts are
started from the main levels in safe ground towards supposed points of
enrichment, where the ore is worked out generally by over-hand
stoping in floors one underneath the other, each consisting of several
approximately circular chambers, which are often 40 to 50 feet in
diameter, and 35 to 45 feet high.
*' Having in the first instance made one of these excavations, the
next step is to drive one or more galleries in any desired direction, just
sufficiently long to leave a safety pillar of comparatively poor rock,
usually 15 to 25 feet in dianieter, between the last chamber and the
nearest point where ore can be found that can be worked in a similar
manner ; and thus a series of chambers is formed, irregularly placed
with regard to one another, on the same storey of massive pillars of
* country rock.' "
Mining in the Zinnwald.
In the Zinnwald District tin ore occurs in a granite rock sometimes
called a greisen ; this rock contains only a small proportion of felspar,
the whole mass is stanniferous in parts, but the richer deposits occur
in concentric zones, about 10 inches thick.
The following section is taken from the " Vereinigt Zwitterfeld,"
by A. G. Charleton, and given in his work on " Tin Mining " (page 49)
FIQ. 29.
It shows admirably the general ribbon-structure of "the beds,"
consisting, as may be seen, of streaks of " pay " (aa), alternating
TIN DEPOSITS OF SPAIN. 169
with parallel layers of barren vein-matter, or country rock ; whilst
underneath " the greisen " (b), that passes into granite (e) and forms
the roof, there is a soft white decomposed layer of kaolin (g), separated
from the filling of the vein by thicik lenticular tufts of green mica
(chlorite) (h) interbedded with very large and perfect crystals of
wolfram and quartz, the latter mineral frequently occurring " capped."
The following account is taken from the " Genesis of Ore Deposits,"
page 54 : —
" The tin deposits of Altenberg and Zinnwald in Saxony have lately
been investigated by K. Dalmer. The cassiterite deposits of Alten-
berg consist, as is well known, of a number of ore-fissures which some-
times carry a notable amount of quartz, mica, and topaz, as well as
cassiterite. Over a considerable area traversed by these veinlets
appears a greisen locally known as z witter, which Mr. Dalmer shows
to have resulted unquestionably from the metasomatic alteration of the
granite. This process consists of a replacement of felspar, principally
orthoclase, by topaz, containing lithium and fluorine.
"The beginning of the process is often visible, small strings of
aggregates of mica and topaz pervading the felspar. These strings
repeatedly cross each other, and by extension of the mineral individuals
complete replacement is attained. The greisen consists of : Quartz,
50-28 ; topaz, 12'14 ; mica, 36-18 ; and cassiterite, 6*43 ; total, 99-65
per cent."
Tin Deposits of Spain.
Although tin has been mined for in Spain more or less since the
time of the Phoenicians, it has never been an important factor in
the tin production of the world. Tin occurs both in the alluvial wash
and in lodes, Mr, James Mactearn, in a report on some alluvial
ground known as the Arnoyaseco alluvial deposit, describes the tin
drift as being more or less sandy in character containing a little clay,
having an average value of about 2-50 kilos of black tin per cubic
metre. The country rock here consists mainly of schists and slates
broken by masses of intruding granite ; quartz veins are found tra-
versing both of these rocks in which occur irregular bunches of
tin ore.
The rate of wages in this district is given as follows : —
Miners
Women and boys -
Carpenters -
Smiths (providing tools) -
Do. (without „ ) -
Bullock cart and driver -
In the provinces of Orense and Ponteredra, the tin deposits occur
over an area of about 12 square miles, and a number of lodes have been
- 1
3 to 1
8 per day.
-
7ito 1
,.
- 2
1 to 2
6 „
-
4
„
-
2
6 „
-
5
„
170 TIN DEPOSITS OP THE WORLD.
intermittently worked here for long periods. The veins carrying the
cassiterite are generally small, averaging about 8 inches, and traverse
the mica scbists and hornblendic rocks in which they occur. The vein-
stone is mainly quartz, mica being present in small quantities, the lode
also carries wolfram and iron pyrites in varying quantities, the tin ore
occurs in irregular masses. * In the province of Salamanca there are,
traversing the older slates, quartz lodes which contain tin ore, and in
1875 tin mines of that region afforded employment to about 70 work-
men.t Near Carthagena tin ore occurs in lenticular deposits in Permian
slate. J Tin ore has also been found in the province of Almeria.§
Tin Deposits of Portugal.
Tin deposits occur in the provinces of Beiro, Minto, and Tras-os-
Montes. Alluvial tin ore is found in the drift, and the working of
these gravels in a small way has been carried on from the time of the
Romans.
The tin occurs in the stockwork formations in the granite, but the
tin ore is irregularly disseminated. Tin is also found in small veins
traversing the slates, and in the province of Tras-os-Moutes some veins
were sunk on to a depth of 150 feet, but the ore was too poor and
irregular to pay, and the work consequently abandoned.
At the present moment the value of the tin output per annum is
under £500 a year in value.
Tin Deposits op France.
Tin has been mined at Pitriac and Lakilleder in Brittany, where the
geological conditions resemble those of Cornwall — that is to say, it is a
district composed chiefly of clay slates corresponding to the killas of
Cornwall. These have been broken through by granite upheavals —
the whole are traversed with porphyry dykes. Serpentine also occurs
in irregular masses.
11 The tin ore is found in small quartz veins, and disseminated in
the rocks themselves at the junction of the eruptive masses and the
altered sedimentary formations. Nothing answering to the strong
masterly lodes of Cornwall has, however, yet been discovered, and all
attempts at mining tin ore on a commercial scale have proved to be
disastrous failures.
At the Moulin de la Villeder, near the rock Saint-Andre, a vein of
stanniferous quartz is enclosed in granite.
* Phillips and Louis, "A Treatise on Ore Deposits," p. 504.
t Massaret, "Ann. Soc. Geol. Belg.," 1876, II., p. 58.
J M. Garcia, "Boletin de la Comision del Mapa Geologico de Espana," III.,
1876, p. 2.
§ "Revista Minera," 1821, p. 148.
II Louie, " The Production of Tin."
TIN DEPOSITS OP itALY, SCOTLAND, ETC. 171
At Pyriac the clay slate is in contact with the granite, and at their
point of junction there are some small veins of quartz in which the tin
ore occurs in irregular bunches.
However, as a tin producer, France is an unimportant factor in the
world's production.
Tin Deposits of Italy.
Although economically unimportant, these deposits possess consider-
able interest. Tin was first discovered in 1875, near Campaglia
Marittima, a small town situated about four miles from the Tuscan
coast and about 35 miles south-east of Leghorn. It was while looking
for iron ore in some ancient excavations that the discovery of the
existence of tin ore was first made. The cassiterite here is associated
with calcite and ferric oxide. The ancient mine is known as the Cento
Camerelle, and has been extensively worked for hsematite. The tin
lode was found about 50 feet west of the ancient workings. The
general strike of the lode was east and west. The cassiterite was in
places replaced by haematite. In 1877 about 20 tons of tin ore was
obtained, but since then nothing of importance has been done, and the
latest mineral returns of Italy show that there is no tin ore produced at
present.
Tin Deposits op Scotland.
The following is an extract by Dr. Flett and Mr. C. T. Clough
taken from "The Memoirs of the Geological Survey," 1903 : —
"In the foliated granite gneiss of Carn Chuiuneag, Ross-shire,
magnetite is found in streaks and veins along two bands which can be
traced for a distance of 100 and 250 yards respectively, and have a
breadth of 10 and 15 yards. Probably there are other localities in
which magnetite occurs, as loose blocks of it, apparently weathered out
of the adjacent rock, are found scattered over the hillside. It is believed
to be a basic segregation, or perhaps a series of veins in the original
igneous mass, but both have been much altered by shearing, and their
exact relationships are somewhat obscure. It is possible that the mag-,
netite veins really belong to the sediments of the Moine series, now
converted into granulitic gneisses and mica schists. In these there are
bands of heavy minerals, which indicate the original bedding, but one
specimen of iron-ore from the Moine gneisses was tested in the labora-
tory and proved to consist of haematite (not magnetite) and to contain
no cassiterite.
" A specimen of the magnetite sent in by Mr. Clough shows that
there is a varying percentage of cassiterite in the rock. Microscopic
sections prove that some parts of the specimen contain very little tin
dioxide, while in others it is abundant. In addition to magnetite and
cassiterite, quartz, orthoclase and plagioclase felspars, muscovite, biotite,
and rutile occur, and these are so distributed as to give the mass a
foliated structure.
172 TIN DEPOSITS OF THE WORLD.
Analysis of Magnetite by Dr, Pollard,
SiO, 7-97
Al,03 - - - - - - -98
Fe,03 6^*69
FeO 25-94
MnO- - -16
CaO - -59
MgO- --.-.. -26
SnO,- -...-. 3-22
H,0 at 105° C. -06
H,0 above 105° C. - - - - '43
Total - - - 100-30
" Alkalies not estimated. No other elements excepting a trace of
Titanium and a doubtful trace of Tungsten were found.
" Magnetite occurs disseminated through the granite in small patches
and isolated crystals of small size, enclosed in the other minerals, but
an examination of the microscopic sections in which it was thought
likely that cassiterite might occur has failed to indicate its presence.
*' Apart altogether from the possible economic importance of this
discovery, about which it is premature to speak, there are certain other
points of interest about it to which reference may be made. It is the
first recorded occurrence of tinstone in Scotland, as though this mineral
is abundant in Cornwall, and has also been found in Ireland, it has not
been hitherto proved to accompany any of the numerous granitic intru-
sions in the Scottish Highlands and Southern Uplands. Moreover, if
the preliminary hypothesis indicated by the facts as at present known
be correct, viz. — that the magnetite and cassiterite are early basic segre-
gations from the granitic magma, the mode of occurrence is of great
interest, and is perhaps unique. Tinstone is mostly found either in
sands and gravels derived from the wear and tear of the lodes, or in
veins and impregnations accompanied by quartz, tourmaline, and
chlorite. If such veins had once been present in the Carn Chuinneag
granite, and had been subsequently torn out and crushed during the
earth movements which converted the granite into a gneiss, they could
not have produced the tinstone and magnetite nodules, for quartz is com-
paratively rare, and tourmaline does not occur. There is evidently
something unusual about these deposits."
Occurrence of Tin in Ireland.*
Tinstone has been found at Ballinasilloga, and on the high ground at
Ballinavally, but it is of no commercial importance.
The Tin Deposits of Mexico.
Uncertain when tin was first discovered in Mexico, but it is certain
the mines were exploited by the Spaniards at an early date. The first
Phillips and Louis, "Treatise of Ore Deposits," p. 312.
TIN DEPOSITS OF MEXICO. 173
exact reference was made in Humboldt's "Essai Politique sur la
Royaume de la Nouvelle Espagne." ''' • I
The export of tin from Mexico in 1903 was o8'o quintals, equiva-
lent to 5,934J lbs*
Tin is widely diffused, but the chief centres of mining are Cacaria-'
and Potrillos, in Durango, and Teocaltiche, in Jalisco.
Potrillos, which is the name of one of the outlying ranches of the
great ranch of Guatimape, is situated in the Sierra de San Francisco, a
span of the Sierra Madre, about 100 miles north of the city of Durango,
and 25 miles from Coneto. All transport except over the main road to
Coneto has to be done by pack animals, horses, mules, and burros.
The general altitude of the valleys of Potrillos is probably 6,500 to
7,000 feet, the crests of the mountaius being 1,500 to 2,500 feet
higher.
The rainfall is very heavy from July to October. The region is
sparsely timbered with pine, scrub, oak, and madroua.
The first can be used for mining timber, and the last two for fire-
wood. The black tin produced was smelted in Potrillos region.
The geology of the Potrillos district is simple. The prevailing rock
is rhyolite and rhyolite-tuff, chiefly the latter. This rock covers vast
areas in the northern and north central parts of Mexico. f Beyond the
limits of the sheet of young igneous rocks a grey, finely crystalline
granite is exposed, and is probably the underlying rock. Cassiterite
occurs in the rhyolite-tuff along the fault planes in aggregations of
nuggets (called guijilos by the native miners), and occasionally in bands
of crystalline mineral, replacing the country rock between two sheeting
planes. With the former the cassiterite is often very finely dissemi-
nated, so that it will not average 1 per cent, of tin. The ore mined is
generally worth 3 to 10 per cent., and is broken from faces 3 to 4 feet
wide.
These ore bodies are exceedingly ill-defined, passing into barren
country rock by insensible gradations.
J In the State of Durango the country rock is generally rhyolite,
rhyolite-tuffs, and quartz porphyries. Some of the mineral associations
common to other deposits are also to be noted here, more especially the
presence of topaz, and of other minerals containing fluorine. On the
other hand, wolfram is rare, and some of the Durango tin ores present
the very curious phenomenon of being intimately associated with anti-
monial and arsenical compounds. Stream tin has been worked, but the
quantity is limited on account of the physical peculiarities of the
country, its steeply-precipitous but narrow valleys, and the small rain-
fall. It seems probable that the greater part of the small amount of
tin-bearing alluvium that could accumulate under these conditions has
already been exhausted, and a certain amount of vein mining has been
done, generally in a desultory manner ; but little tin in the aggregate
* Paris, 1827, Tome III., 308, and Tome IV., 76.
f These rocks were identified by Prof. J. F. Kemp.
X Louis, " The Production of Tin."
174 TIN DEPOSITS OP THE WORLD.
has yet been obtained, and apparently there has been no systematic
prospecting.
The following account of the SaiQ Alto Tin Deposits, by J. Nelson
Nerius, was taken from the Engineering and Mining Journal of
20 June, 1903 :—
" The mountains south of Sombrerete and west of Sain Alto, in the
State of Zacatecas, Mexico, have been frequently mentioned in connec-
tion with deposits of tin ore. The region yields a small amount of this
metal annually, but it is much less than is commonly supposed.
"The mountains are all of rhyolite, which has been forced up
through the vast thickness of thin-bedded shale and limestone, generally
accredited to the Cretaceous age. The rhyolite is quire uniformly rifted
in a general north-westerly direction, and the fracture planes thus pro-
duced give access to the circulation of water which occasionally causes
considerable decomposition of the rhyolite along the fractures and the
impregnation of oxides of iron, manganese, and tin. Small chambers
have been found along these seams from which a few tons of good tin
ore have been extracted. No regularity in the occurrence of such
deposits has been determined, and none can logically be expected to
occur. In these seams the tin oxide is badly adulterated with iron and
manganese oxides.
" In many places bands of the rhyolite occur carrying amygdaloid s
of chalcedony. Such outcrops are frequently mistaken for vein indica-
tions. Along with this chalcedony occasional nodules of cassiteidte are
to be found, which, after weathering out of the rock, becomes concen-
trated in the deep ravines. This is the source of most of the tin
produced in this district. The native ranchmen, during and after the
rainy season, search the ravines and recover the ore. Nearly all of it
is picked by hand from crevices in the rocks over which the streams
flow. The natives pay little attention to the small banks of gravel,
although, by panning, these yield a very small amount of fine ore. The
sides of the ravines are so abrupt that no gravel deposits can accumulate
along them. Where the streams leave the mountains and flow out upon
the surrounding plains, large areas of sand and gravel have accumulated,
and it" is possible that these deposits may contain valuable amounts of
tin ore. At present the ranchmen recover all the available ore from the
stream beds, and the seams in the rhyolite are not sufficiently promising
to warrant development, although several claims have been denounced
(taken up) upon the neighbouring mountains.
" Amygdaloidal deposits of chalcedony occur in other parts of Mexico
in rhyolitic formations along with cassiterite ; apparently they can be
regarded as an index when searching for that ore.
" The following statistics were compiled from the bills of sale of
metallic tin purchased in Sain Alto during three years, which documents
were courteously loaned by the purchasing agent. The grade of ore is
taken at 40 per cent., because considerable of the ore smelted in those
years came from some of the old mines. The iron and manganese in the
ore as mined reduced the grade and made the charge refractory in the
furnace.
tin deposits op the united states of america.
Metallic Tin Purchased in Sain Alto.
175
Year.
Weight of
Metallic Tin-
kilos.
Price per kilo.
Mexican
money.
Total Value.
Grade of Ore
(estimated).
40 per cent.
40 per cent.
40 per cent.
Weight of
Ore in kilos
1900 -
1901 -
i902 -
201-60
441-00
146-70
» -925
1-169
1-140
»186-48
516-53
166-10
11868-11
504-00
1,102-02
364-25
788-30
1,970-27
" As nearly as could be ascertained, the sales in Sain Alto represent
about one-third of the profluction for the years mentioned. The larger
producers sell their metal at higher figures to actual consumers in
Zacatecas and Mexico City. Therefore the production of tin ore from
this region was about as follows, stated in short tons : 1900, 1*5 tons ;
1901, 3-5 tons ; 1902, 1 ton. No figures are available for the current
year, but a few tons will be smelted after the rainy season."
It seems probable that, though tin ore occurs very widely distributed
throughout Mexico, there are few, if auy, individual rich or important
deposits. No statistics of production are obtainable from Mexico ;
statistics of exports and imports show figures fluctuating consider-
ably, but always small, whilst the imports appear always to exceed
the exports, so that the country is not quite self-supplying. As, how-
ever, imports and exports together never seem to reach 100 tons a year,
the matter is quite unimportant, and it will be best to simply look upon
Mexico as merely a potential small contributor, bnt not an actual
contributor, to the world's supply of tin.
Tin Deposits of the United States of America.
The total amount of metallic tin produced from ore mined in the
United States has not exceeded 200 tons, though small amounts have
been found in no less than seventeen States and Territories ; Alabama,
Alaska, California, Colorado, Connecticut. Georgia, Idaho, Maine,
Massachusetts, Missouri, Montana, New Hampshire, North Carolina,
South Dakota, Texas, Virginia, Wyoming.
In Alabama, cassiterite occurs in quartz veins in graphite schists *
near granite, and as disseminated grains in gneiss.
In California,t small amounts of float cassiterite have been found in
the gold placers at a number of widely separated localities. The ore
* Phillips, Wm. B., " Geol. Survey of Alabama Bull," No. 3, 1892.
t " Sixth Ann. Rep. California State Min. Bureau," Sacramento, 1886,
** Eleventh Ann. Rep. Califoinia State Min. Bureau," Sacramento, 1893. Fairbanks,
Harold W., "Tin Deposits at Temescal," Am, Jour, Sci., 4th Ser., Vol. IV., 1897:
pp. 39-42. Rolker, C. M., "Production of Tin in Various Parts of the World.
Sixteenth Ann. Rep. U.S. Geol. Survey," Pt. III., 895, p. 536.
176 TIN DEPOSITS OP THE WORLD.
is found in places at the Temescal mine, five miles south east of River-
side. At this place there is an area of hornblendic biotite-granite over
two miles in diameter, which is cut near its borders by dykes of highly
quartzose and felspathic fine-grained granite. The ore occurs in
veinlets of tourmaline and quartz aggregates which run north-east and
south-west through the granite. A great body of such vein matter,
covering an area 300 by 250 feet, and 25 to 30 feet high, crops out in
the Cajalco Hill. What is known as the Cajalco vein courses north-
east from this outcrop, and the workings extend for 1,000 feet along it.
The vein is sinuous, and varies from a minimum of a clay seam to a
maximum of 8 feet. There is always a clay gouge on one and often
on both walls. Two hundred and ninety-one and fourteen one-hun-
dredths pounds of metallic tin were produced from ore mined at Temes-
cal previous to 1892, when the mines were riband oned.
In the Carolinas a tin belt * extends in a nortli-east-south-west direc-
tion for about 31 miles, and lies partly in North Carolina and partly in
South Carolina. Tin ore is not evenly distributed through this distance,
though the tin-bearing formation, which consists of crystalline schists or
gneisses containing pegmatitic dykes, is continuous. The rocks of the
tin belt are very much decomposed, and the pegmatite dykes are very
thoroughly kaolinized. The tin ore has been found loose in the soil, in
the gravels, in boulders of quartz and mica, and occasionally in the
pegmatite dykes. The most promising deposit on the belt is at the
Ross mine, near Gaffney, S. C., from which 34,471 pounds of the ore
were shipped in 1903 ; 75,000 pounds shipped in 1904 assaying 66 per
cent, metallic tin.
In Colorado tin ore has been reported near Golden, but little is
known of its occurrence.
In Connecticut tin ore has been found at Haddam, but only as a
miueralogical curiosity.
In Georgia tin ore has been reported from Lumpkin County, as
occurring in granite and chlorite schists, with minute quantities from
the gold washings.
In Idaho a few specimens of stream tin have been found on Jordan
Creek, in the south-western part of the State, and in the Coeur d'Alene
district.
In Maine + a cassiterite occurs at Winslow in small veins, which
traverse impure limestone, with purple fluorite, mica, quartz, and mis-
pickel. These veins have been prospected to a depth of 100 feet, but
have yielded no tin in commercial quantities. Similar occurrences are
reported at Paris and Hebron.
In Massachusetts a few crystals of cassiterite have been found with
albite and tourmaline at Goshen and Chesterfield.
* This note is furnished by Joseph Hyde Pratt in advance of Economic Paper,
No. 8, of the North Carolina Geological Survey on " Carolina Tin Deposits."
+ Jackson, C. T., " On the Discovery of a New Locality for Tin Ore in Winslow
Me. : Proceedings, Boston Soc. Nat. Hist.," Vol. XII., 1869, p. 267. Hunt, T. S.,
" Remarks on the Occurrence of Tin Ore at Winslow, Me. : Trans., Am. Inst. Min,
Eng.," Vol. I., 1873, p. 378.
TIN DEPOSITS OF THE UNITED STATES OP AMERICA. 177
In Missouri * a small amount of cassiterite has been found replacing
sphene in granite.
In Montana,! stream tin has been found in Prickly Pear, French Bar,
and Ten Mile Creeks, in the " Basin," in Basin Gulch and in Peterson
Creek. Light-brown, rounded pebbles of wood tin associated with topaz
crystals have been found at one locality.
In New Hampshire cassiterite was found at Lynn and Jackson, in
1840, by Dr. Jackson. It occurs with arsenical and copper pyrites,
fluorspar, and phosphate of iron in small quartz veins, and mica, slate,
and granite near a trap dyke.
In South Dakota, J the Black Hills contain noteworthy deposits
of tin ore, which, however, have not yet proved commercially produc-
tive. They occur in an area of coarse-grained granite in the central
part of the hills. The Etta mine deposit, the only one that has pro-
duced any considerable quantity of tin, is a lenticular body of pegmati-
tic granite, which consists of quartz, felspar, (albite) lepidolite, and
spodumene in individuals of great size, up to eight or nine feet in dimen-
sions. Cassiterite occurs in association with lithia, mica, and is accom-
panied by columbite and tantalite, with which it is apt to be confused.
The mine was sold to an English Company, which erected a 250 stamp
mill, but the ore did not prove profitable to work, and after the first run,
which produced 9,385 pounds of tin, the work was closed.
§ Although there has been no appreciable development of the
Harney Peak properties, the Tinton Tin Company, controlled by
Chicago interests, has been working during the last two years on its
claims situated in what is known as the Nigger Hill and Beer Gulch
districts, west of Deadwood and Lead, S. Dak., and 75 miles north-
west of Harney Peak. This new district is partly in Lawrence County,
S. Dak., and partly in Crook County, Wyo., being on the border line of
the two States. The Tinton Tin Company have been working a small
concentrating plant, but, owing to the lack of proper smelting facilities
in the United States, they have shipped to European ports for treatment
a carload of concentrates said to contain an average of 62*5 per cent, of
metallic tin. One parcel of the Company's property, 140 by 50 feet,
and another 90 by 6 feet, yielded an average mill return of 1*16 per
cent, of metallic tin, which was 0'16 per cent, greater than the assays
of hand samples made in the laboratory. The quantity of ore so far
treated has averaged 1 per cent, of metallic tin, and the concentrates
therefrom have ranged from 62*5 to 65 per cent, of metallic tin.
In Texas, II tin has been discovered in quartz veins, occurring in
greisen granite in the Franklin Mountains near El Paso, and one small
* Raymond, R. W., " Trans., Am. Inst. Min. Eng.," Vol. I., 1873, p. 374.
t Ibid.
I The writer is indebted to Mr. S. F. Emmons for the note on tin ia South
Dakota.
§ " Board Trade Jour." 1905.
Dumble, E. T., " Second Ann. Rep. Texas Geol. Survey," 1890, pp. 595, 690,
713
M
/
178 TIN DEPOSITS OF THE WORLD.
crystal has been found at another locality. At El Paso, * wolframite
occurs with the ores, and felspar is replaced by cassiterite.
In Virginia,! good tin prospects have been found on the headwaters
of Irish Creek, Rockbridge CouDty, in quartz lenses and stringers in
granite, which itself is intrusive in metamorphic schists. Associated
minerals are wolframite, mispickel, iron pyrites, quartz, and beryl, with,
small amounts of siderite, limonite, chlorite, muscovite, damourite, and
fluorspar.
In Wyoming, at| Nigger Hill, in the north-western portion of the
Black Hills, cassiterite has been found in a granitic area that is similar
in geological association to that at the Etta mine.
Tin Deposits of the York regions of Alaska. §
The steady advance in the price of tin within the past few years,
coupled with the enormous and increasing consumption of this metal in
the United States (the American Tin Plate Company alone already
using over $7,000,000 worth per annum), has naturally greatly stimu-
lated the search for tin ores in the United States, with a view to
rendering this country less dependent on foreign sources of supply.
Probably the most extensive development work has been carried on
in North Carolina and South Carolina. One mine in South Carolina
has already produced over 60 tons of tin concentrates. Considerable
stream tin has for many years past been found in the ravines and streams
of South Carolina, but during the past year quite extensive mining has
been conducted in the immense pegmatite dykes that traverse the
granite and slate areas of the Carolinas.
Quite recently veins of tin ore in granite have been discovered in
the State of Texas near El Paso. The tin is said to be of high quality,
and the prospects look extremely good for the amount of development
done.
The old Temiscal Tin Mine near San Diego, in the southern end of
California, is now being operated under lease, and the lessees report a
having of 2 per cent, black tin from the tailings of the former works.
The proprietary (English) company formerly did extensive development
work on a capital of $100,000, with the inevitable result that the com-
pany became involved and the works were closed down. Tin exists in
the veins, which are quite numerous, but it is not yet satisfactorily
settled whether the tin occurs in quantities that would pay even with
the most modern methods and machinery and the best management.
The occurrence of tin-bearing lodes in the bed-rocks iias been verified
by the Geological Survey at poiuts known as Lost River and Cape
* Rolker, C. M., *' Production of Tin in Various Parts of the World : Sixteenth
Ann. Rep. U.S. Geol. Survey," Pt. III., 1895, pp. 523-525.
f Rolker, C. M., op. cit.
t Ibid.
§ Arthur J. Collier, " Gov. Geological Survey of U.S. America."
TIN DEPOSITS OP THE YORK REGIONS OF ALASKA. 179
Mountain. The occurrence of alluvial tin (placer deposits) has been
confirmed on Anikovik, Buhner Creek, a tributary of the Anikovik,
and on Buck Creek, a tributary of Grouse Creek, which flows through
Mint River into the Lopp Lagoon.
Tin ore has also been reported from a great many other localities
which have not been thoroughly examined by geologists. The tin
deposits, as far as known, do not follow any definite system, and are
confined to no particular belt or zone.
The succession of rocks as far as determined is as follows : — The
oldest sediments are limestones which are white and usually crystalline.
They are often beautifully banded and occasionally have intercalated
bands of mica-schist. This bed of limestone is near the coast, and is
about half a mile in width. Cape Mountain is made up of a mass of
granite which has intruded into limestones. Along the crest of the
mountain, pillars and pinnacles of granitic rock are common, and are due
to the existence of a double system of jointing. The granite, except for
this jointing, is entirely massive and usually coarsely crystalline. Near
the margin of the mass it contains large ciystals of felspar. To the
north of the limestone a *belt of slates and siliceous schists about five
miles in width has been mapped, whicb are regarded as overlying the
limestones conformably. The evidence of conformity is that the strikes
have a general parallelism to those limestones and the dips are variable,,
suggesting about the same amount of folding as has taken place in the
limestone belt. These slates, and especially the schists, are usually tra-
versed by numerous joint plains by which they are split up into rhom-
bohedral forms. These beds are occasionally calcareous, but more often
graphitic. With the slates, series of greenstones of varying descrip-
tions are frequently found. These greenstones are usually massive as
though they had suffered some jointing like that found in the slates.
They are apparently largely of a diabase character. To the north-east
of this slate series, and overlying it, there was found a belt of earthy
limestone with some slates; These rocks seem to be less altered than
the slate series, though they are apparently conformable. Only a few
exposures of this rock were studied, however, and no details can be
given.
The unconsolidated deposits of this region can be classified as (1)
river and stream gravels, and (2) bench gravels. The first include the
gravels and sands of the flood plains of the streams and rivers. The
bench gravels are marine deposits which were laid down during the
epochs of submergencj.
The known occurrences of tin ore will be described under the head-
ings " Lost River," " Cape Mountain," " Buck Creek," " Buhner Creek,"
and "Anikovik River."
* Lost River. — Lode tin deposits have been found four and five miles
from the coast on Lost River. Its two tributaries. Tin Creek and
Cassiterite Creek, enter from the east about three miles and four miles
* " r.S.A. Geological Survey," Series A., Economic Geology, 33, 1903.
M 2
180 TIN DEPOSITS OF THE WORLD.
respectively from its mouth, and tin ore has been found on both of these
Creeks.
A white porphyritic dyke, cutting the limestone four and five miles
from the coast, forms the present point of interest to the tin miner.
This dyke, which is about 100 feet wide, has been traced from Tin
Creek on the east, to Cassiterite Creek on the west, a distance of about
a mile. Tin ore has been found on the outcroppings of this dyke, and
distributed along the surface of its course. Some of the ore is highly
siliceous, and carries small crystals of black cassiterite, whilst orher
specimens of the ore are clearly of granitic origin. The cassiterite in
this ore occurs as disseminated crystals of varying size, the accompany-
ing minerals being tourmaline, pyrite, galena and garnet.
A specimen of placer tin ore (alluvial) obtained near the outcrop-
pings of this dyke consists mainly of cassiterite, wolframite and garnet
being present. The evidence in regard to this deposit shows it is in
part at least essentially an altered granite porphyry (greisen) having
crystals of cassiterite disseminated through it. The greisen forms a dyke
which has been followed from Cassiterite CreeiJf to Tin Creek, a distance
of 6,000 feet. Some crosscuts have been made near Cassiterite Creek
on this dyke, and the width given approximately at 100 feet ; but it
has not been possible to ascertain its true value up to the present.
Cape Mountain. — The Cape Mountain Tin Deposit occurs in a high
peak which marks the western point in America.
The ore obtained here differs in appearance from that on the " Lost
River." Large pieces of pure cassiterite, several pounds in weight,
have been found, and these specimens show no outward signs of crystal-
lization.
The tin ore was discovered in Cape Mountain in July, 1902, and
extensive developments were planned for 1903,* but owing to a break-
down in machinery these have been delayed.
Buck Creek. — Buck Creek is the scene of the first attempts of tin
mining in Alaska. This Settlement is 20 miles north-east of York, and
4 miles from Lopp Lagoon, an inlet from the Arctic Ocean. Buck Creek
is a small stream, ^ye miles in length, running into this Lagoon.
Mr. Edgar Richard, in the Engineering and Mining Journal for
January 3rd, 1903, reports that the source of the cassiterite can be
readily found in the slates of the Potato Mountain range in countless
small veins or vugs, the denudation of the slates leaving the cassiterite to
be concentrated into the alluvial deposits.
The gravel deposits in the bed of Buck Creek average from 100
to loO feet wide, except in a few greenstone boulders found in the
mouth of Satter Creek. They consist of slate and quartz together with
other minerals derived from the country rock, such as hasmatite, limonite,
magnetite, ilminite, pyrite, cassiterite, and a small amount of gold.
Cassiterite in the form of stream tin is distributed from the mouth of
the creek to within a mile of its head, the ore varying greatly in size.
The ore from the workings near the mouth of Buck Creek is gene-
rally well rounded, while that obtained near the creek is sharp and
TIN DEPOSITS OF THE YORK REGIONS OP -ALASKA. 181
angular. The ore varies in colour from black to light resin or amber.
A number of specimens were obtained that showed pieces of quartz and
slates from the bed-rock still attached to them ; and some small pieces of
cassiterite have been found enclosed between fragments of slate, showing
that they were broken out of small veins in the slate. Fannings
made a^t the head of Buck Creek gave an average value of 8 lbs. of
60 per cent, ore to the cubic yard.
On the evidence of prospectors it seems that this uniform distribu-
tion through the gravel prevails generally along the creek.
The gravel deposits on Grouse Creek, below the mouth of Buck
Creek, seem worthy of attention. They are more extensive than those
on the Buck Creek, but the amount of tin ore is reported to be very-
small.
Outside the creek bed there is a covering of moss and debris above
tlie gravel, and no ore is known to be found on the hill-side. The thickness
of the tin-bearing gravel varies from a few inches to five feet. Several
companies are actively engaged in exploring claims on the Buck Creek,
but the methods of mining and sluicing the stream tin are still some-
what primitive.
The first discoveries of tin ore in the York region were made on the
Anikovik River and Buhner Creek, a tributary of this river. In the
lower part of the Anikovik River, there are rather extensive gravel
deposits; the bed-rock consists for the most part of slates.
Buhner Creek has a length of about a mile, and flows in a sort of
V-shape gullet, cut in the slates. On this creek, the stream tin is found
concentrated on the bed-rock with other heavy minerals. The sample of
the concentrates from the sluice box yielded the following minerals: —
Cassiterite, magnetite, ilminite, liminite, pyrite, phlorite, garnet and
gold. The determination by percentage of weight is as follows : —
90 per cent, of tinstone ; 5 per cent, magnetite ; and other mhierals
5 per cent. ; but these workiugs have now been abandoned, as the
minerals were not found in sufficient quantities to pay, but might be
made to yield fair returns if economically worked on an extensive scale
by hydraulic methods.
Discoveries of tin-bearing lodes have been reported by prospec-
tors from many other localities in Steward Peninsula, some of which
deserve notice, since geologic conditions are known to be promising.
These localities are Brooks Mountains, near the head of Lost River,
four miles north of Lost River Tin Deposits ; the hills east of Don
River ; Ears Mountain, about 50 miles north of Port Clarence ;
Hot Springs, about 70 miles north-east of Port Clarence ; Asses
Ears, about 20 miles south of Kotzebue Sound ; and the Diomede
Islands in Behring Strait, about 30 miles off Cape Prince of Wales
Island. The above facts show cassiterite to be regularly distributed
through an area of 4oO square miles, embracing the western end of
Steward Peninsula.
The tin ore is almost all cassiterite, though a little stanuite has
been found at one locality. The matrix of the tin ore is in deposits of
at least two essentially different types. In the one it is in quartz veins,
182
TIN DEPOSITS OF THE WORLD.
which cut phyllites or metamorphic slates ; in the other the cassiterite
is disseminated through more or less altered granitic rocks. This
second type of lode deposit is the one which gives promise of commer-
cial importance.
I.EGENO
Sands and gravels
Limestone and sqhlstS
Slates
Port Clarence limestone
Granite
[=1
Granite-porphyry dikas
Scale
15 20
30 miles
Fig. 30.— Geological Sketch map op the York Region.
TIN DEPOSITS OF THE YORK .REGIONS OF ALASKA. 183
In estimating the value of tin ores in this northern region, several
facts should be borne in mind. The region is utterly without timber,
and is accessible by ocean steamers only from June to the end of
October at the longest. Harbour facilities are poor, and all supplies
and wages are high. On the other hand, the construction of railroads
and wagon roads is not difficult, and will require comparatively smnll
outlay. All of the occurrences described are within a few miles of tide-
water. Freight rates to Paget Sound ports should be very low, as the
large fleet of ocean steamers which run to Nome return empty. Last
summer upwards of 98,000 tons of freight were brought to Alaska by
vessels that called at Nome. It is fair to say that these tin deposits
are well worth careful and systematic prospecting.
( 184 )
CHAPTER XV.
MOUNT BISCHOFF TIN MINE.
The Mount BischofF Tin Mine is situated in the north-west of Tas-
mania, about 45 miles from the north coast ; there is a gradual ascent
nearly all the way. The top of the mountain where tke miue is
situated is 3,500 feet above the sea-level, and 1,200 feet above the
surrounding table-land of basalt.
This mine was discovered by James Smith on the 4th December,
1871. While prospecting for gold and silver, he found a heavy, dark,
resinous-looking substance iu the bed of a creek ; and presuming from
its specific gravity that it was a metallic ore, he carried some of it to a
distance of 54 miles to '.rable Cape in order to have it tested. There
he learnt, somewhat to his disappointment, that the heavy mineral did
not contain either of the precious metals, and was simply tin ore.
Mining was begun in December 1872, and in August, 1873, the present
Mount Bischoff Tin Mining Company was formed, with a capital of
£60,000, in order to prosecute working on a larger scale.
The property at first consisted of 160 acres, covered for the most
part with dense horizontal scrub ; this consists of a tangle of twigs and
branches almost impenetrable to the explorer, and often concealing soft
and treacherous mossy bogs. As the carriage of supplies over the then
existing rough bush track cost from £24 to £30 per ton, a road to the
nearest port. Emu Bay, became a matter of necessity. In 1875 the
work was completed, and though, owing to the imperfect method of con-
struction and the excessive rainfall, it was impassable for nine months
in the year, it nevertheless enabled goods to be carted to the mine in the
dry season at a cost of £6 to £8 per ton. A horse tramway, constructed
in 1884, reduced the freight to £5 per ton, and finally its conversion
into the present railway of 3 feet 6 inches gauge brought about a further
reduction to £3 per ton, which is the present tariff, except for specially
rated articles.
The geological features are very interesting, and the origin of this
remarkable deposit has been made the subject of much discussion.
Mount Bischoff consists of contorted and greatly metamorphosed slaty
rocks, which are traversed by dykes of topaz and quartz porphyry.
El
©
(9 ¥
MOUNT BISCHOFF TIN MINE. 185
The surrounding plains are largely formed by sheets of basalt. Within
an area of 1,100 yards by 600 yards around the mountain the dykes are
of a stanniferous character ; but bsyond this distance they become more
compact, harder, and less prolnctive. The remarkable deposits of tin
ore which form the wealth of Mount Bischoff are probably due to the
disintegration of the stanniferous dykes.
Bai-on von Groddeck,"^ late Director of the Royal Prussian Academy
of Mines at Clansthal, has carefully analysed the tin-bearing porphyries
of Mount Bischoff, and ho concludes that the tin matrix is not, as
supposed, a quartz porphyry, but a porphyritic topaz rock, and that, like
the topaz rocks at Auerbach in Germany, they form in themselves
immense lodes of tin ore.
The Mount Bischoff t deposit has been more recently described by
W. von Fircks in a paper, in which he writes as follows : — " The tin
deposits appear in an area of quartzites and clay slates with dykes of
quartz porphyry. Granite is present, but at some distance from the
mine. These deposits are in part fissure veins carrying cassiterite,
pyrite, arseuopyrite, fluorite, wolframite, tourmaline, and siderite. The
latter mineral is notable because not usually present in veins of this
character. Another part of this deposit is formed by replacement,
chiefly of porphyry dykes. All rocks in the vicinity of the mine are
much altered. The schists and slates contain a considerable amount of
tourmaline and are in part changed to typical * tourmalin-fels ' by
complete replacement, only a few grains of the original rock remaining."
Where the dykes have intruded into the schists, the rock has been
much twisted and folded, and some jemkrkably clear anticlinal sections
have been exposed in the various excavations and cuttings. In one
instance a pure topaz dyke was discovered on the southern section of
the mine. It was about 3 feet in thickness when first opened, and
contained a high average of black ore.
A very noticeable feature is the presence of iron pyrites close to the
surface in the " Slaughter-yard Face," while no pyrites was met with
in the "Brown Face " until a depth of 200 feet was reached.
For the sake of convenience the deposit will be described in detail,
in six bodies known locally as the Don and Stanhope Sections, White,
Brown, Slaughter-yard, and Alluvial North Faces.
The Queen Lode, situated north-east of the brown face, is a separate
body of ore, having an average width of 3 feet 6 inches, and gives a
uniform return of 12 per cent, of tin ore. The production for the first
half-year of 1904 was 142 tons.
The Brown Face has been so named from the colour of the deposit,
and formed by far the larger portion of the payable ore worked. This
face rests (m a bed of slate at an angle of 35°, and the ore in this face
■ has averaged about 2f per cent, of tin ore ; it is a mass of stanniferous
gozzan, and is probably the result of decomposition, i?i situ, of a large
ore body consisting of iron pyrites and cassiterite. In several portions
* Johnson, *' Geolooy of Tasmania," p. 221.
t Zeitschr. d.d. Geo. Ges. Bd, U., p. 433, 1899.
186 TIN DEPOSITS OF THE WORLD.
of tlie face large bodies of undecomposed pyrites exist, but their general
average is lower than that of the gozzari.
The White Face is a deposit of detrital tin ore extending over a large
space, the average thickness of which is about 25 feet ; it contains
from 2 to 3 per cent, of cassiterite fairly evenly distributed ; in some
parts the constituents are sharp and angular, and sometimes well
rounded and water-worn. This deposit rests on a bed of. micaceous
clay of varying thickness, which again rests on a stratum of iron pyrites
much decomposed near the clay ; this pyrites rests on slate towards the
north, but in the south part on the older alluvium, consisting of water-
worn fragments of chalybite, iron pyrites, blende, and argillaceous
matter ; this older alluvium covers a considerable area on the south side
of Mount Bischoff, but it is not, howevc, stanniferous.
It is not necessary to give a detailed description of the Slaughter-
yard Face, which resembles the other faces, the only difference being the
gozzans are more siliceous in character. On the Stanhope Section some
large porphyry dykes are being worked ; this ore, though very much
harder than the gozzans, carries payable ore for 63 feet in width in places.
There has been some good alluvial found on the northern side of the
mountain ; the full length of the face opened here is 191 feet, with a
depth of 144 feet. A cut on the east end was made 22 feet wide by
56 feet in height, and on the west another cut was made 23 feet wide
by 56 feet in height. Near the surface of these cuts the wash was
very good, especially the capping, which contaiued a fair percentage of
nuggets of solid ore. The green lode situated north-east of the Brown
Fa -e is a separated body of ore, having an average width of 3 feet
6 inches, with a uniform return of about 12 per cent, of tin ore. At
the 180 foot level bunches of pyrites have been met with, the ore up
to this point being entirely free.
A tunnel has been driven underneath the Brown Face right through
the mountain, but disclosed nothing of great value, as the Brown Face,
at a depth of 260 feet, splits into innumerable veins, consisting mainly
of iron pyrites carrying a little cassiterite.
About a mile to the north of Mount BischoiF a lode, known as the
North Valley Lode, has been worked by the Bischoff Company ; this
lode varies from 1 to 5 feet in width, and near the surface is free from
pyrites, but as depth is attained the ore becomes highly pyritic, the
ore occurring in shoots which carry at times as much as 50 per cent, of
cassiterite, but the average of the ore throughout is slightly under
1 per cent. Work has been suspended here for the time being.
The method of mining the ore is as follows : — The various faces
and suuh portions of the porphyry dykes as are rich enough to work
are mined as open quarries in the soft ground. Every miner can exca-
vate from 10 to 12 tons of ore per day, but only about 4 tons in the
harder porphyry dykes. The rates of wages are 8*. per day for miners,
and 7*. to 7^. 6d, per day for truckers and labourers. The total cost of
mining and delivering the tin stuff to the Company's dressing-sheds is
3*. 2^d, per ton. The water supply, although naturally good, has had
to be artificially increased at the Waratah Works ; for motive power
MOUNT BISCHOFF TIN MINE. 187
and dressing purposes a total of 41,60'J gallons of water are used hourly;
this is drawn from the Waratah River and the Fall Creek, on which
extensive reservoirs have been constructed. They have been formed
by building embankments across the gully, and have a storage capacity
of 490,000,000 gallons, and a total sum of £22,395 has been spent on
the increased water supply.
"^Dressing, — The principal dressing works are at Wanitah, a place
conveniently situated as regards water supply, about 1 J miles from the
mine. At the mine the coarser stuff is reduced in a jaw-breaker to a
diameter of 9\ inches, and is then deposited in hoppers, to which the
fine stuff is run direct. From these hoppers the ore is taken in bottom-
discharging trucks to the dressing works, on a railway of 3-foot gauge,
with steel rails weighing 46J lbs. to the yard. This has been worked
by a locomotive since 1879, when it took the place of a previously
existing horse tramway. The cost of transport by the horse tramway
was 4Jrf. per ton ; now it is but slightly more than Id. per ton.
The tin ore brought by the locomotive is first pHSsed through stamps,
and is then sorted by up-current rising classifiers into coarse and fine
qualities, which are jigged in two-compartment jiggers. The overflow
from the classifiers flows to settling tanks, from which the slime passes
to rotating tables, and the overflow to the concave buddies which are
placed on the lower floor. From the rotating tables tbe concentrates
are delivered into troughs, and are afterwards re-treated on tables and
finally keeved, while the tailings are led to buddies. The heads from the
buddies are re-buddled and finally cleaned in a keeve. The concentrate
from the first compartment of each jigger is clean ore ready for the
smelter ; it is caught in troughs underneath the jiggers. In the second
compartment a mixed product collects, consisting of cassiterite with
adherent waste ; this is removed by a hydraulic-jet elevator and is jigged
a second time, while the tailings are concentrated by buddies, the concen-
trate being pulverised in one of two Chilian mills, then cleaned on
rotating tables and buddies, and finally prepared for the smelter by
keeves. From the second jigging the concentrate goes to the smelter
as second-class ore, while the tailings go to the Chilian mills above
mentioned. The whole of the tailings are re-worked in separate sheds,
where, after classification, the sand goes to buddies and the slime to
rotating tables.
The stamps are of the Calif ornian type ; there are three batteries of
forty, twenty, and fifteen heads respectively. The moving part of each
stamp weighs 5 cwt., the lift is 8 inches, and the number of blows
72 per minute. There are five heads in each mortar-box, the order of
lift being 1, 4, 2, .^, 3. The screens are of woven steel wire, with
196 holes to the square inch (14 mesh), two to each box ; they are
19 inches long by 12 inches wide, and require renewal every eighteen
days. The shoes, which weigh when new 128 lbs. each, have an
average life of six months ; the dies, of 70 lbs. weight each, require
renewal once a year. Although the water acts corrosively on the shoes
* Kayser and Provis, "Trans. Inst, of Civil Eng.," Vol. 123, Pa>t I.
188 TIN DEPOSITS OF THE WORLD.
and mortars, the tin-stuff is more easily stamped than ordinary Coraish
tin-capels. The crushed ore does not discharge freely on account of its
adhesive nature ; and consequently only sufficient water is used to
produce a good splash, more water being added to the pulp before it
reaches the classifiers. During the dry season, when water is scarce,
shoes of 64 lbs. weight are used. This method of reducing the amount
of ore dressed is better adapted to the arrangement of the works than
stopping a part of the plant.
It is necessary to mention that th^ tin ore is associated with other
mineral substances, which have specific gravities only slightly inferior
to it, and that therefore careful classification is imperative. There are
in all thirty of these classifiers, and they are used in tandem pairs ; the
first separating coarse sand, while the overflow carries away the slime.
They are constructed of pine boards, 1 J inch thick, tongued and grooved.
Water under pressure is brought into a horizontal pipe under each
classifier ; the pipe and the classifier being connected by a vertical pipe
through wliich water flows upwards, and the classified product down-
wards. The latter is delivered into a jigger by a vertical pipe attached to
a prolongation of the horizontal pipe. The mouth of the delivery pipe is
12 inches above the bottom of the classifier. In the horizontal pipe,
between the classifier and the jigger, is a " gauge piece," which is
simply a short iron block, screwed at both euds, and bored with a hole
f 6 -inch in diameter, inserted to prevent an undue quantity of the water
going to the jigger. This device is a great improvement on the ordi-
nary cocks formerly used, which suffered so much from the wear of the
sharp sand that they became inefficient in a day or two. A wooden
plug in the end of the horizontal pipe and the hand-valve are both
provided in the event of the appliance becoming choked.
Jigging is performed through the sieve, and there are thirty two-
compartment Hartz jiggers. The cases are of 2^-inch pine, tongued and
grooved, the whole being held together by ^-inch bolts. The sieves are
2 feet 6 inches long by 1 foot 6 inches broad ; woven steel wire of fine
mesh rests for support upon a stouter sieve, the two being attached to a
wooden frame which rests upon an iron grid, and is held in position by
a bar fixed above it. The pistons are of wood, aud are caused to
reciprocate by eccentrics, the throw of which can be altered at will.
The arrangement is similar to that already described by Mr. E. du Bois
Lukis.* The connecting rod is made in two pieces, united by a long
coupling nut, so as to allow easy access to the interior of the jigger
without interfering with any other part of the machine.
The hydraulic-jet elevators used to convey the mixed products from
the second compartment of the first jiggers to other jiggers are shown
in detail (Fig. 30). This system of continuously withdrawing the
concentrates from the second compartment, and saving the second-class
ore separately, enables a better-dressed product to be obtained from the
* " The Separation of Galena and Blende from their Gangue as practised at the
mines of Sentein, Arlege, France," Minutes of Proceedings Inst.C.E., Vol. LXXXV.
1885-86, p. 364.
MOUNT BISCHOFF TIN MINE.
189
first compartment ; it also acts as an indicator of the regularity of the
working of the jigger, any irregularity being shown by a variation in
the amount of discharge from the second compartment. The jets work
^2^2222221
^Z23RS33SS
FIG. 31.— SBOTION OF HTDRAULIC JET ELBVATOR.
silently and with little attention ; the nipple, the only part liable to get
out of order, can be replaced in less than five minutes. The jiggers
working on coarse sand have sieves with 144 holes to the square inch
(12 mesh), and are driven at 160 strokes of yV-i^^ch per minute ; while
those on fine sand have sieves with 196 holes to the square inch
(14 mesh), and make 202 strokes of |-iuch per minute. The sand
delivered to the jiggers 'carries 5 to 12 per cent, of tin oxide, and the
jiggers save between 65 and 75 per cent, of the output from the
Waratah works ; the ratio of second-class ore to first class being 1 in
10. It is necessary that both sand and water be fed to the jiggers with
the utmost regularity, that the classification be efficient, and that the
fragments of ore constituting the bed be of uniform size.
There are thirty-nine convex rotating tables in use for treating
slimes. They are similar in principle to the first table described by
Mr. R. E. Commans in a Paper * read before the Institution of Civil
Engineers. The surfaces of the tables are now made of cement, as it was
. found impossible to keep the wood surfaces previously in use sufficiently
even. The frame is of wood, on which is fastened sheet iron, -jV-inch
thick, to carry the cement surface, which is 1 inch in thickness ; an even
edge at the circumference being secured by a tire of ^-inch pine. When
the cement is well set, it is strong enough to support its own weight ;
and, although the sheet-iron foundation corrodes, and in course of time
altogether disappears, the efficiency of the table is in no wise impaired.
A coating of a mixture consisting of 25 per cent, turpentine and 75 per
cent, coal tar is laid on with a brush when the cement is sufficiently
dry to absorb it. This prevents the corrosion of the surface, which
was found to take place before this precaution was adopted. The
coating requires renewal ouly once in two years. The tables vary in
diameter between 10 and 15 feet, and the slope of the surface is 1 in
* "Minutes of Proceedings InstCE.," Vol. CXVI., 1893-94, p. 57.
190 TIN DEPOSITS OF THE WORLD.
12. The slime deposited on the table is swept off at the required points
by jets of clean water. The tailings are removed by the first jet, and
afterwards the concentrates, two classes being made in the first treat-
ment of the slime, and three in the final treatment of concentrated slime.
In order to enable the attendant to vary, as necessary, the point at
which each jet of water strikes the table, the nipple is bored at an angle
to its axis, so that by slightly turning it round the direction of the jet
can be changed. The jets at each lable require 23 gallons of clean
water per hour. Frequently two or three tables are mounted on one
axle ; and when space or motive power is limited, this arrangement is
to be recommended. In the case of a double table, the concentrate
made by the upper table is further cleaned by the lower one, and with
favourable ore this may be sufficient treatment before the final tabling ;
but when the ore is more difficult to treat, a third operation may be
necessary, and this is especially the case with very fine slimes.
The tables are rotated by worm-gearing once in 2^ minutes ; and a
single table will treat 7 cwt. of slime per hour, requiring ^ horse power
to drive it. The double and triple tables consume very little more
power than the single tables. The slime, as delivered to the rotating
tables, carries between 0*1 per cent, and 1*0 per cent, of tin ore, and the
first concentrates contain between 15 per cent, and 20 per cent. Of the
total output from the works, 15 per cent, to 20 per cent, is saved by
the tables. The cost of constructing and erecting a single table is
about £93 at Mount Bischoff, where labour and materials are alike
expensive.
There are 17 Kayser concave buddies. They are similar to those of
the Munday type, except that, while in the latter the two scrapers
attached to each arm sweep out two separate circles, in the former
the two circles overlap, and so enable the process to be more efficiently
controlled. They are between 14 feet and 20 feet in diameter, and,
working at a speed of 6 J revolutions per minute, require |-H.P.
each. The slime and sand feed to the buddies contain about
0.25 per cent, of ore. The first huddling raises this to 7 per cent., and
by rebuddling the percentage of ore is raised to 60 per cent. The
buddies contribute 4.75 per cent, of the ore saved in the works.
Motive Power. — Seven overshot water-wheels, ranging from 18 feet
to 40 feet in diameter, supply the necessary power for driving the
machinery at the Waratah works. They are so placed, one under the
other, that the water which passes over the top wheel goes to the
second, and then to the third, and so on to the last. These wheels
furnish 200 horse-power. Overshot wheels are used in preference to
turbines or Pelton wheels, because they require less skilled supervision ;
further, because the water employed comes from other dressing sheds
above and is more or less charged with sand, which would quickly wear
out either of the two latter machines.
Lighting, — Incandescent electric lamps are employed; a 120-lamp
dynamo serving to light the works, workshops, and offices. The annual
cost, for maintenance only, of 75 16-candle power lamps is £47 \ls.6d. ;
MOUNT BISCHOFF TIN MINE. 191
while 37 12-candle power kerosene lamps, which were formerly in use
for lighting the dressing sheds, cost for maintenance £112 14*.
Cost of Dressing. — In the BischofF dressing sheds there are 37 men
and boys employed, 13 day, 12 afternoon, and 12 on night shifts. They
are employed as shown in the following table :
1 Attending machinery and supervising
3 Feeding 60 heads of stamps, each - - -
1 „ 15 heads ?> v * * "
3 Attending jiggers, each - - . -
2 „ tables, „ - - -
1 „ buddies „ - - - -
1 „ tables and buddies and lime sheds -
1 Day shift — general work - - - -
The cost of stamping, dressing, bagging, and delivering the ore at
the railway is 1*. IJ^rf. per ton of stuff treated ; this includes labour,
lighting, oil, grease, repairs, and renewals. About 6,000 tons of ore are
treated every month.
The average per cent, of ore obtained from the whole mine is 1 '322.
The cost of mining, crushing, and dressing a ton of stanniferous material
is as follows : —
s.
d.
9
2
8
7
6
7
6
o
6
5
6
6
8
d.
Mining, including new works, maintenance, and
other expenses
Filling, hauling, and emptying trucks
Crushing, dres*sing, and maintenance of plnnt -
Slime sheds
Ringtail sheds ------
Management and supervision - - - -
Plant, including all machinery . - .
Development and progressive work - - -
Diamond drilling
Waterworks -------
Ore bagging
Stores --------
Sundries -------
The dressed ore is sent to the company's smelting works at
Launceston, a distance of 160 miles, in two qualities ; No. 1 quality
assaying, on an average, 70^ per cent, metallic tin, and No. 2, 65 per
cent. It does not pay to dress cleaner than this, as the cost of extra
labour, and the additional -losses incurred, would more than counter-
balance the increased value of the purer ore.
Tailings and Loss. — After the tailings leave Waratah works they
are again treated, together with those from two neighbouring companies'
works, at the *' Catch 'em" sheds, f mile further down the stream
Here they are first huddled, then crushed in a Chilian mill, classified
2
10-836
5-566
9-962
1-171
2-111
7-479
2-052
2-627
7-224
0-031
0-527
5-630
0-717
6
7-933
192 TIN DEPOSITS OF THE WORLD.
and treated on rotary tables. One man and one boy are employed in
each shift, and about 50 tons of ore are saved annually, ^'umerous
assays have been made to ascertain the amount of eassiterite in the tailings
after they have been finally discharged ; but the results differ according
to the source of the tin-stuff. The material from the White Face is
easily treated, and the loss is extremely small ; but it is more difficult
to extract all the ore from that yielded by the Brown and Slaughter-
yard Faces — the difficulty apparently bearing some relation to the amount
of haematite present. Samples taken every day for a fortnight averaged
between 0*01 per cent, and 0*2 per cent, of tin, the higher limit being
reached only in one sample.
Auxiliary Works, — Until recently some alluvium was partially
dressed at the mine by sluicing. The concentrate, which contained
about 20 per cent, of tin ore, was sent to the Waratah works for final
treatment ; while the tailings from the sluices were re-treated at the
Ringtail works, situated a little below the mine. Now most of the
material adapted for this treatment has been worked out, the sluices are
no longer used, and the Ringtail works are only run occasionally to treat
the tin-stuff washed down with the drainage from the mine. There is
another dressing establishment at North Valley, which, although
smaller, only differs in general arrangement from the Waratah works in
that it has a calciner for roasting the ore which is pyritic.
The inconvenience due lo the distance of the mine from all engineer-
ing works led to a brass and iron foundry being established at Mount
Bischoff in 18S7. This has proved extremely useful, both in preventing
stoppages and in enabling old material to be worked up again and mixed,
so as to produce metal best suited to the particular purposes in view.
A No. 1 Root-blower provides the blast, and also blows four fires in the
smithy. A telephone connects the office with North Valley, 3 miles
away, the Ringtail dressing-sheds, the mine, and the manager's house.
Ore obtained since the formation of the company, 65,376 tons
18 cwts. 2 qrs. 2 lbs.
Total dividends declared to 30 June, 1906 (including No. 351),
£2,061,000.
In November, 1906, the output of the Moimt-Bischoff Company
was reduced from 100 tons of ore a month to 60 tons. This was
caused by the exhaustion of the richer ore without making due prepara-
tion and alterations in the dressing plant necessary to treat the large
masses of low-grade ore profitably. A new electric power plant is
being installed, and a more up-to-date mine equipment. This will have
the effect of reducing the working costs per ton, which have been
steadily rising for some years past.
Tin Dressing, — Ore treatment at Mount Bischoff, Tasmania.
Donald Clark outlines the Mount Bischoffi tin concentrating plant.*
The system used is as follows :
(1.) Stamps (896 lbs.) with 14-mesh screen, stamping 4 tons per
stamp per 24 hours ; the pulp goes to (2).
* "Australian Mining Standard." Vol. XXIX, 1903, p. 432.
MOUNT BISCHOFF TIN MINE. 193
(2.) Spitzluttn, yielding spigot product to (3) and overflow to (4).
(3.) Five No. 1 Hartz jigs, yielding concentrates to a bin, middlings
to (5) and tailings to (6).
(4.) Spitzkasten yielding first, second and third spigot products to
(9), overflow to waste.
(5.) Five No. 2 Hartz jigs yielding concentrates to bin, middlings
to (8) and tailings to (6).
(6.) Five buddies yielding concentrates to (7) and tailings to
waste.
(7.) Chilian mill ; product to (8).
(8.) Five slime tables yielding concentrates to (9) and tailings to
waste.
(9.) Five Kayser ore-dressing tables, yielding concentrates to (10)*
tailings to waste.
(10.) Dolly tub, concentrates to bin.
( 194 )
CHAPTER XVI.
THE DOLCOATH TIN MINE.
This mine is still the largest tin-producer in Cornwall, and has during
the 150 years of its existence produced minerals to the value of over
£6,000,000 ; it was known as an ore-producing mine as early as
1746, and has been worked successfully for both tin and copper. It is
now, however, exclusively a tin mine ; an interesting fact is that it is
probably the only mine in existence that has been managed by one
family for three generations.
The present company operating the mine was formed in 1895 with
an authorised share capital of £350,000, and has erected the present
mining and dressing plant ; also conducted the mining operations on an
extensive scale.
Mr. R. J. Frecheville gives the following particulars of the Great
Main Lode of Dolcoath. (Trans. Royal Geo. Society of Cornwall, 1887.)
To the south of the town of Camborne, where the killas overlaps the
northern base of the granite range of hills known as Cam Camborne,
Carn Entral, and Carn Brea, the formations are traversed by the great
main lode of Dolcoath, Cook's Kitchen, Tincroft, and Carn Brea Mines,
which, together with its branches, produces about one-third of the total
amount of " black tin " raised annually in the county, and is now being
worked on continuously for a distance of about 2^ miles along
its course, and to a depth in Dolcoath Mine of 485 fathoms, from surface
on the " underlay," or 355 fathoms perpendicular.
The " strike " of this great lode, which goes by the name of the
Main Lode in Dolcoath, Chappie's Lode in Cook's Kitchen, and the
Highburrow Lode in Tincroft and Carn Brea Mines, is about 30^ north
of east, approximating closely to that portion of the line of the West
Cornwall Railway connecting the towns of Camborne and Redruth.
Its " underlie " is to the south, and varies considerably, being much
flatter in the deeper workings than it is nearer surface. Thus in
Dolcoath Mine, from the 200 fathoms level to the bottom of the " sump,"
the " underlie " is 4' 6^' in the fathom ; and in Cook's Kitchen Mine
from the 190 to the 345 fathoms level, it is 3' 3^' in the fathom ; whilst
in both mines in the levels above the " underlie " averages about 2' in
the fathom.
THE DOLCOATH TIN MINE. 195
In the " country " south of the main lode there are several powerful
branches also " underlying " south, but steeper than the main lode, so
that in time they drop into it and serve to enrich it. Of these the most
important are Dunkin's Lode and the South Lode, the former being
known as Teague's Lode in Cam Brea.
These lodes all " crop up " within the killas ground at surface, but
penetrate the granite at various depths, ranging from about 80 fathoms
from surface at New Shaft in Carn Brea to about 130 fathoms from
surface at the engine-shaft in Dolcoath, the line of division between
the granite and killas thus appearing to incline to the north-west.
In the following remarks on the mines in which the main lode is
being worked, the numbers prefixed to the levels signify their depth in
fathoms on the *' underlie" of the lode, taken from the adit level, which
comes in at from 20 to 30 fathoms from surface.
In Camborne Vean, the western mine of the group, the engine-shaft
has been sunk on the main lode ta the 180. From that level a cross-
cut has been driven to the south lode, on which a shaft has been sunk
to the 282. Operations are now, however, confined to above the 140, to
which level the mine is drained by Stray Park engine. The lode shows
itself here strong and masterly, composed chiefly of capel (schorl-rock),
quartz, and peach, with a very small admixture of tin oxide.
At the 364 level the lode in the Dolcoath Mine was about 20 feet
wide, and a large proportion of the lode-stufi*, both here and in the
bottom of the shaft, contained an average of about 10 per cent, oxide
of tin to the ton of stuff.
The cross section, which is taken through the engine shaft, shows
the branches which have dropped into the main lode from surface down.
The great improvement in the bottom levels may be ascribed to the
influence of the south lode, itself a most important lode, which fell into
the main lode at the 375 level. There are, however, two points con-
nected with Dolcoath that are to a certain extent overlooked. East of
New East Shaft the main lode is standing almost intact from the
230 down, the south lode having been chiefly worked on in this portion
of the mine. Again, west of Old Sump Shaft below the 190, there has
hardly been anything done on the south lode. Now, there can be little
doubt, judging from the developments made on the main lode at the
352 level east of New East, and on the south lode at the 364 level
west of Old Sump, that these unexplored portions of the mine contain
valuable runs of productive ground.*
The characteristics of the lode stuff in Dolcoath are that the richest
ore consists of a compact, bluish -coloured rock, consisting of a mixture
of peach, quartz, and schorl, with strings of oxide of tin running through
it, while the poorer parts are more capelly and of a blacker colour.
Where chiefly composed of quartz the lode is very poor. In the
100 shallower levels the lode was much harder than it is at present.
On the north or " foot-wall " side the lode has always a distinct and
* At present the New East Shaft has been sunk to the 455 fathom level, and
the mine has been extensively developed and worked from here.
N 2
196 TIN DEPOSITS OF THE WORLD.
definite wall ; whilst on the south side it passes gradually into
non -stanniferous granite, without any clear and definite bounding-
plane.
The granite in the deeper portions of the mine has a bluish colour
for a couple of fathoms from the lode, and after that a greyish colour.
East of New East Shaft at the 352 level, for about 50 fathoms in length
on the south lode, the granite on the hanging-wall side is quite soft and
decomposed, so that the level has to be closely timbered ; and the lode
presents, considering the depth from surface, an extraordinary appear-
ance. It is full of " vugs," can be broken with the pick alone, and,
being stained of a reddish colour with oxide of iron, looks, as an old
miner remarked to me, just like the " back " of a lode. On the foot-
wall underneath this soft ground the lode is extremely rich, and shows
signs of great tranquillity, the peach, quartz, and tin oxide lying more
or less in parallel layers. Luckily the occurrence of this very soft
granite enclosing the lode seems to be quite local, the end of the
352 level east being now driven in hard ground. The granite showing
in the 364 level and in the bottom of the engine-shaft is also hard and
firm.
Cook's Kitchen Mine, to the east of Dolcoath, is separated from
the latter by a cross-course filled with decomposed granite and clay,
between 8 and 9 feet wide, nearly perpendicular, and coursing about
north 40° west.* This cross-course heaves the lodes from 70 to *
80 fathoms to the right.
J, H. Collins, in his " Origin and Development of Ore Deposits,"
gives the following account of the Dolcoath Mine : —
The average width of the Dolcoath lode is certainly much greater
than the average of the lodes of tin and copper in the west of England
as given by Mr. Hen wood. From the 66 to the 197 in Dolcoath it was
about 6 feet, but narrowing in places to 1 foot, and widening in others
to 16 feet. At the present bottom of the mine it varies between 2 and
4 fathoms, with perhaps 16 feet for an average ; the tinny portions
being mostly wider than those containing only copper, as already stated.
In Cook's Kitchen, Tincroft, and Cam Brea Mines, the present average
is somewhat less. On the whole I think we may safely take the mean
width of the whole lode at 6 feet for the coppery portions and 10 feet
for those yielding tin (of which the leader or actual fissure filling will
not average more than one foot) for the whole period since the mines
have yielded tin. The lode in the lower levels has widened out, and is
now being worked from 20 to 40 feet wide, the quality of the ore
being much poorer.
The walls in the great lode are generally fairly distinct, but less so
in depth than nearer " grass." The hanging wall is generally better
defined than the foot wall, especially in the deeper w^orkings. Vugs
and cavities were much more common in the lode in the shallower
* Richard Thomas, " Eeport on a Survey of the Mining District of Cornwall
from Chasewater to Camborne," 1819.
THE DOLCOATH TIN MINE. 197
than they are in the deeper workings, but they are still occasionally
met with in all the mines on the lode.*
The contents of the lode have, as already stated, varied at different
depths. In the shallower portions above adit there was much gozzan,
consisting of earthy brown iron ore with iron pyrites and spongy quartz,
and in places earthy black copper ore, with various rare crystallized
arseniates and phosphates of iron and copper, also much chalcopyrite
and chalcocite. In the eastern part of the mine a good deal of tin was
raised from the shallower workings. Some of the earthy brown iron ore
was found as far down as the 197 fathom level. The rich parts, while
yielding copper, usually gave it as chalcopyrite with few crystals. Soon
after reaching the granite most of the copper gave out and the mine
changed to a tin mine. The richest ores of tin are of a bluish colour, not
very hard but quite compact, and permeated in all directions by strings of
rather light-coloured oxide of tin. Often this bluish rock passes into a
■ dark red ferruginous mass without becoming poorer in tin. Careful
microscopic examination shows that the blue tin-stone, apart from the
tin, consists of quartz, chlorite, and schorl — the latter mostly in-
minute needles ; and the change from blue to red seems to be a sub-
sequent oxidation change of the chloritic portion of the mass.t The
poorer parts of the lode are very similar, except that they are very
much harder and more siliceous, and with a tendency to a black or light
blue colour.
The country rock changes noticeably with the lode matter. The
killas is fairly soft near the surface ; it generally becomes harder as it
approaches the granite, but is always soft near the rich parts of the
lode ; above it is often yellow or buff in colour, below mostly deep
blue. While the granite remained very hard, the lode was not produc-
tive either for tin or copper — it is now in general fairly soft and moist,
the felspar much kaolinized and often accompanied with pyrites and red
oxide of iron.
The curious alternations of killas and granite which this great lode
cuts through have been noticed by many writers. In 1882 "a large
mass of hard slaty rock was met with in the 352 fathom level east of the
eastern shaft . . . included in the granite 240 fatht^ms below the point
where that rock was first cut into by the workings . . . this resembles
the ordinary killas of the district, and on comparing thin sections of the
two under the microscope their identity becomes at once apparent. "J
The imagination is struck with the figures expressing the extent
* In November 1814 a cavern was discovered in the main lode at a depth of
170 fathoms. It was from 18 to 20 fathoms high, and from 4 to 9 fathoms wide.
It contained much loose material which had fallen from the sides, and communi-
cated by narrow channels with many subsidiary cavities. See " Trans. Koy. Geol.
Soc. Corn.," Vol. I. Similar vugs have been found in nearly all the master lodes
of the West of England. The present manager of Dolcoath, Mr. Arthur R.
Thomas, informs me that the deep levels do not bear out Mr. Collins deductions,
as there are no well-defined walls, and he would rather class the deposit there as
a big zone of impregnation. — S.F.
f See " Cornish Tin-stones and Tin-capels," plate IV., figs. 3-4.
X Phillips, " Ore Feposits," pp. 131-2.
198
TIN DEPOSITS OF THE WORLD.
and produce of this great lode. But if we look at the facts in another
way, as suggested by M. Moissenet, we shall see how insignificant a.
feature it forms in the earth's crust. " Let us suppose a model of the
lode made to a scale of one-thousandth the real size — it could be easily
ma<ie from a sheet of lead 12 feet long and 3 feet wide. In many places-
the thickness would have to be reduced to a mere film, but in some it
would require to be thickened up to a quarter of an inch or a little more.
The sheet might be placed on edge, its length in a direction nearly
north-east, south-west, and with a considerable dip to the southward.
If now it were bent lengthwise in such a way that the thicker portions
were more nearly east-west, and the thinner more north-east, south -west^
and also bent in width so that the thicker portions stand more nearly
vertical than the thinner, and the lower portions more nearly horizontal
than the upper, it would very fairly represent the relative proportions
of the lode and also its position in the ground.* Viewed in this manner
the vast and richly filled subterranean channels, which by the imple-
ments of the miner are transformed into caverns of imposing extent,,
appear what they are — as thin veins in the ground."
Some of the stopes are of an immense width, which has necessitated
a hanging tram-road, a feature in the mine, as not much timbering is
required, the country rock being very hard.
The system of working by contract in the stopes is carried out, and
also in the developing work in the mine, the contractor supplying-
explosives, rock drill, tools, and all labour at a fixed price for ore
delivered at the shaft, the company supplying the power for the
rock drill and paying all winding expenses. Contracts are mainly
set to a group of men (pare), generally 18, who break the tin-stuff
and deliver it to the surface free of all charges to the company, who,,
however, supply the men with stores, explosives, candles, etc., at cost
price, and charge the winding costs to the pare (this is the local
name for the contract party of miners). The development work is
chiefly carried out by contractors, who supply their own rails, drills, and
general stores, the company supplying the compressed air free of charge*
Output of Dolcoath Mine.
1888 -
1889 -
189D -
1891 -
1892 -
1893 -
1894 -
1895 -
1 «96 -
1897 -
Tons of
lack Tin.
2,239
1898
2,215
1899
2,027
1900
2,132
1901
2,536
1902
2,421
1903
2,126
1904
1,766
1905
2,038
1906
2,095
Tons of
Black Tin.
- 2,302
- 2,084
- 1,962
- 1,968
- 1,657
- 1,687
- 1,705
- 1,697
- 1,748
* The actual fissure or leader, apart from its metalliferous capels, might be
represented on the above-mentioned scale by a sheet of paper thickly or thinly
coated with lead on each side, in accordance with the dimensions given above.
Photo &y]
IBurrowSf Camborne.
HANGING TRAMWAY, EOLCOATH TIN MINE.
THE DOLCOATH TIN MINE.
199
Table of the Result of Stamps on Dolcoath Tin Mine,
. Cornwall,
(From information supplied by Mr, John JRowe, Engineer to the Company,')
Speed.
Pneumatic Stamps.
138 blows per mi-
nute.
Galifornian Stamps.
90 blows per mi-
nute, ordinary
cams.
Cornish Stamps.
Speed -
70 blows per minute;
revolving axle with
three cams, 14 re-
volutions per mi-
nute.
Drop -
10 inches -
10 inches -
10 inches.
Screens
400 mesh (37 Cor-
nish).
400 mesh (37 Cor-
nish).
400 mesh (37 Cor-
nish).
Feeding
Challenge ore
feeder.
Challenge ore
feeder.
Hand fed.
Weight of stamp -
1,250 lbs. -
950 lb'.
850 lbs.
Kesult for 24 hours'
stamp
20-1516 tons
32 cwt.
22 cwt.
Continuous run of
• 636 hours for one
stamp.
533-333 tons
533 tons 3 cwt.
qr. 3-584 lbs.
42-272 tons -
42 tons 5 cwt. 1 qr.
18-48 lbs.
29-104 tons.
29 tons 2 cwt. qr.
8-96 lbs.
Cost of crushing per
ton.
16-31 1(^. -
20-203^. "
22-76^.
One Pneumatic Stamp equals 11-8 of 960 Calif ornian Stamp.
950 lbs. Californian Stamp is the one used on the Rand, crushing 4 tons per
24 hours.
The manganese jaw-rock breaker lasts 4 months on the Dolcoath and 10 months
on the Band.
On Crushing and Concentration at Dolcoath Mine, Cornwall,"^
Previous to the installation of frue vanners, the usual system of tin
dressing in Cornwall was in vogue at Dolcoath Mine.
After stamping, the pulp was, up to a few years ago, passed into
"strips" immediately in front of the Cornish stamps, these strips being
troughs about 20 feet in length and 18 inches in width and depth,
having an incline of about 1 in 30. A partial concentration was thus
effected, and a considerable proportion of the slimes separated by over-
flowing.
Three products resulted from this operation, which were further
dressed in buddies. The slimes passed direct into settling tanks, and
after a sufficient time had elapsed for proper settlement were treated
* R. Arthur Thomas, " Trans, Inst, of Min. and Met,," March 15, 1899.
200 TIN DEPOSITS OF THE WORLD.
over self-acting frames, the concentrates from which were again settled
and further treated by girls over dead frames. The first products from
this washing were " huddled " until the heads contained about 25 per
cent, black tin and then calcined.
The " strips " have been entirely dispensed with, the pulp now being
passed into a classifier, the fines from which are concentrated on a
revolving table, thus dispensing with the slime treatment mentioned
above. The table has a slow revolving bed sloping towards the centre,
and is divided into two parts, in order to make two classes instead of
one as previously. The inclination varies, but as a rule is 1 : 12.
The overflow from the revolving table on being settled contains
enough slimes to be automatically treated at a profit over self-acting
frames.
The coarse sand from the classifier is run through an ordinary
huddle, from which three products are obtained : (1) heads, (2) middles,
and (3) tails.
The " heads " are usually sent at once to the calciner. The second
and third products are again " huddled " until a sufficiently high product,
about 25 per cent, black tin, is obtained, which is calcined.
Brunton's calciner, the type in use, is a rotary furnace revolved at
varying speeds, depending on the nature of the stuff to be roasted.
After calcination the concentrates are again huddled and " kieved,"
until a marketable product is obtained.
The huddle separation shows fairly good results, but entails an exces-
sive amount of labour ; the system can only be defended on the ground
of being already established, or the difficulty in obtaining the neces-
sary capital required for making a change for the better. And
again, the actual is greater than the apparent loss in treatment, be-
cause of the many re-handlings of intermediate products. As a result
of the introduction of more automatic machinery, apart from the frue
vanner plant, considerable reductions have been made in the cost of
extraction.
About 12 months ago experiments were made with the idea of still
further reducing this amount of labour, and getting by automatic
machinery sharper separation, and consequently more economical results.
In these experiments two systems of dressing were tried : —
(1) Classification, and subsequent treatment of the fines over a
convex revolving huddle, and the roughs over two percussion
side-inclined belts.
(2) A single treatment over vanners without classification.
In order to test the capacity and efficiency of the various machines,
the trials were carried out on tin-stuflf varying in character and value,
and extended over a period of three months.
Two 4-foot vanners took the pulp from a five-stamp mill, the ore in
every case being carefully weighed, sampled, and assayed.
Ten stamps supplied the pulp for the other machines. The concen-
trates from all the machines were weighed, sampled, and assayed. The
percentage of extraction was thus accurately ascertained.
THE DOLCOATH TIN MINE. 201
With the first system very good results were obtaiued, but too many
products requiring further re-treatment, and further consequent losses,
were produced.
As the vanner in taking the pulp direct from the stamps without
any handling or classification produces a good clean concentrate at one
operation, which is higher than that made by the other machines, and
with small loss in the tailings, it was found to be the most suitable.
The mill crushing for this vanner plant consists of 60 stamps of the
ordinary Californian pattern, and fitted with suspended Challenge
feeders and a few roller feeders.
Forty of them have a falling weight of 850 lbs., the other 20 heads
1,050 lbs. each.
In addition to the 60 heads, there are two heads of Husband's
pneumatic stamps, having a capacity equal to about 20 heads of
the California 850 lbs. stamps. The mill is, therefore, equal to 80
stamps.
The motive power is a horizontal compound condensing engine,
having cylinders 17-inch and 28-inch and 48-iDch stroke, made by
Price. The horse-power developed is 143. Steam is supplied by
three Cornish boilers, each 6 feet by 30 feet, working at a pressure of
1031b. per square inch. These boilers have recently been fitted with
Meldrum furnaces, in order to increase their steaming power.
Steady driving being absolutely essential for the vanners, an engine
10-inch by 14-inch stroke, vertical type, was erected to do this work
alone. This engine condenses in the compound engine condenser. A
pumping engine (horizontal) and an electric light installation are used
in connection with this plant. The engines are in one engine room,
and are under the control of one man in each shift.
The ore is screened, selected, and crushed to 1^ cubic inches in the
stone-breaking and sorting shed, near the main winding shaft, and is
then trammed into the mill ore bins. Owing to the extreme hardness
and toughness of the ore, great difl&culty has been experienced in
getting jaws to stand. Manganese steel is now being used with good
results.
The stamps are set with an 8-inch drop, and are run from 85 to 90
blows per minute. Punched copper screens (round holes) are used in
the mill, and are No. 37 Cornish mesh, equal to 27 wire mesh. As the
bulk of the loss of tin occurs in the slimes, it is a point of great import-
ance to arrive at the limit of the mesh of the screens and weight of
stamps with efficiency of subsequent extraction. Experiments are now
being made to determine whether by still increasing the weight of the
stamps more slimes will be produced.
The average daily crushing of the whole mill is 125 tons (2,240 lbs.).
Various forged and cast steel shoes have been tried, but hard cast-
iron made by local founders have worked out at a lower cost per ton,
allowing for re-melting of the old castings when worn down.
The tin ore is exceedingly difficult to crush, as it contains but a
small percentage of friable quartz and a very large proportion of tin
capel, which is both hard and tough.
202 TIN DEPOSITS OF THE WORLD.
The poorer grade ores are the hardest, and contain tlie greater pro-
portion of fine tin. With the present price of black tin 1 per cent, ores
are profitably worked with this plant. The richer ores crush faster,
and need more careful concentration.
The vanner plant consists of 27 6-feet machines with plain belts,
having Brownell patent flanged edges*
In the preliminary trials of corrugated belts against plain belts, the
former were found to bring up too much coarse material, reducing the
percentage of tin in the concentrates.
An ample number of vanners has been laid down so as to efficiently
handle the pulp when the mill is crushing the highest grades of ores.
The method of dressing adopted is a single treatment on vanners,
with re-treatment of the tailings after classification, the slimes on
revolving buddies, the coarse by concentration and pulverising.
One side of the mill, consisting of six batteries of five stamps each,
is supplied with 12 vanners, the other side also 30 heads, has nine
vanners, or three to each 10 stamps. The pulp from the two heads of
pneumatic stamps is led on to six vanners.
The richer grade ores, sometimes running as high as lo per cent, of
black tin per ton, are crushed on the side of the mill having the
12 vanners, two to each five stamps. The vanners are run at 192 re-
volutions per minute, and are spaced at 10 feet 6 inches, with a 6-foot
passage way between their heads.
The main water service (3-inch and 4-inch galvanised piping) is
brought over the passage way on the girders carrying the counter
shafting, with 1-inch brauches to each machine ; similar branches are
carried down at either end and in the middle of the shed, for washing
down the floor, which is. sloped J inch to the foot from the centre of the
passage way.
The vanners are set on sills, on pitch pine 10 inches deep and
8 inches wide. These were bedded in 2 inches to 3 inches of concrete,
in order to make them bear all aloug their length, and to give a wider
bearing on the ground, which was "made" under the outer row of
machines.
A launder having two compartments, each 10 inches deep, is laid all
around the vanner floor. The inner one catches the washings from, the
floor, and the outer one receives the overflow wash water from the
belts. This launder is set perfectly level, so that the water can be
drawn off* at any point of the circuit.
The tailings launders are under the floor, and have a grade of
f inch to the foot. They empty into a cross launder, which takes
the tailings to the classifier.
Wooden swing gates, which can be held in any position by a wedge,
are put in the launders to regulate the amount of pulp to each machine,
or if necessary to cut it off" entirely from any machine during temporary
stoppage.
The delivery from the launder to the distributor is by means of a
IJ-inch hose, which has brass hose couplings at each end, screwed
THE DOLCOATH TIN MINE. 203
firmly on to corresponding parts that are attached to the launder and
distributor.
A short launder from the battery delivers the pulp on to a " grating"
box (punphed zinc screen) at the edge of the battery floor, to prevent
" gravel " from getting on to the vanner belts.
Two men in each shift (four in all) attend to and regulate the
vanners, in addition to which there are two men employed in repairing
the machines. These six men per 24 hours attend to the whole of the
concentration work as far as the vanners are concerned. There is a
general foreman over the whole mill.
The concentrates are drawn and assayed every day. Samples of the
tailings from the belts are taken every day, and after 24 hours are
allowed for settling the water is decanted, and the sample assayed.
The average value of the concentrates is 50 per cent, black tin per ton,
the black tin containing 65 per cent, metallic tin.
A higher concentrate can be made, but it is found that the loss of
fine tin in the tailings increases when making a higher grade con-
centrate.
About one ton of slime tin is produced per month from the settling
boxes taking the overflow wash- water from the concentration troughs.
This product is excessively fine.
The loss of tin in the tailings amounts on the average to 3 lbs. per
ton of stuff*.
The percentage of extraction thus shown on the vanners is a little
over 94 of the gross contents, as ascertained by assays with the vanning
shovel.
The concentrates from the vanners are calcined, and further treated
by washing, in order to get a marketable product. Endeavours have
been made to produce a concentrate that can be sold direct to the
smelters without burning, but as yet unsuccessfully, as the concen-
trates contain too much fine waste and coarse sand, which reduces
the parcel beyond the payable limit. This, however, may yet be
worked out.
The cost of producing a concentrate containing about 25 per cent,
black tin for calcining by the old method at this mill was Is. 3d. per
ton of stuff* stamped. The cost of treatment by vanners, including all
labour, steam, stores, maintenance (at the rate of 6^ per cent, per
annum), interest on the capital expenditure (5 per cent, per annum), is
under 6d. per ton.
The vanner produces a concentrate that contains twice as much
black tin per ton as by the former system, the after treatment of which
is in proportion reduced ; and the total loss in the whole tailings^
allowing for the former re-treatment of intermediate products, is doubt-
less less under the new system than with the old.
( 204 )
CHAPTER XVII.
TIN CRUSHING AND DRESSING MACHINERY.
The old Cornish stamp is still in use in many of the mines in
Cornwall, not because it is an effective machine, but the mines
operating it are too poor to justify the cost of a more modern form
of battery ; it is an exceedingly interesting survival of the early days
of crushing by machinery.
The stamp heads are 7 inches by 11 inches, and the mortar box
has no bottom, a hard bottom being formed with the crushed ore being
beaten into the ground.*
The chief feature to be urged in its favour is the low cost for
maintenance and repairs. When the present machines are worn out,
or the mines operating them are worked out, this machine will be
relegated to the crushing * appliances of the past.
The Californian type of stamp battery occupies in tin mining the
same position as it does in gold mining, and supplies the means by
which by far the largest quantity of tin ore is crushed.
There are various types of these machines on the market, which
differ slightly in design and construction, and it is an easy matter to
ascertain which particular design is best suited to the ore to be
crushed.
In erecting a battery it is absolutely necessary to secure a good
firm foundation ; the following is the usual method employed : — The
vertical mortar blocks are sunk in a pit to a depth of 6 to 10 feet,
according to the position, and well packed all round with concrete.
When the ground is unreliable horizontal foundations spread over a
considerable area are necessary.
The framework of the battery can be either made of wood or iron,
the advantage of using wood being that a certain amount of elasticity
is obtained. Iron frames last longer, but the constant vibration has a
tendency to loosen the bolts, thus causing trouble.
* Latterly at Dolcoath bottoms similar to the Californian stamps have been put
in, and increased the capacity of the mill by 29 per cent.
TIN CRUSHING AND DRESSING MACHINERY. 205.
The mortar box is constructed of cast-iron and weighs about
2,400 lbs., a useful size being 4 feet high, 15 inches broad, and
4 feet 6 inches long, the bottom being 3 inches thick. Screeus may
be made of copper, iron, or sheet steel, and are fixed in frames about
3 inches above the top of the dies. For crushing tin ore usually a
very fine screen is used, generally about 30 mesh.
The weight of the stamp depends on the ore to be crushed, but
about 850 lbs. is found a useful general weight for crushing tin ore.
Pneumatic stamps are in use on the Dolcoath Mine in Cornwally
where they give very good results, but at present they have not come
in for general use on account of the difficulty of repair and requiring
skilled attendance for their successful operation. Extensive improve-
ments are being made, and the general effectiveness of the stamp will
be increased.
Huntington Mills have (in the author's experience) done excellent
work on the reduction of soft dyke material carrying tin ore, but cannot
be recommended for the crushing of the harder sorts of tin stones and
capels.
The principle of the Huntington Mill is : the rolls are not fixed od
parallel shafts pressed together by buffers, but suspended vertically,,
crushing by centrifugal force, which is brought into action when the
frame on which they are hung is set in motion.
The chief advantages claimed are the saving in the cost of the
machine, in the cost of transport and erection, and the rate of discharge.
There are various types of Ball Mills, but in the author's experience
several machines that have been erected on tin mines have since been
discarded for the battery.
The ore when crushed to pulp is variously handled. At the Mount
Bischoff* Mine it is first passed into double trough-rising classifiers, and
then into two-compartment Hartz jiggers. All jigging machines take
advantage of the law based on the fact that if two bodies of equal
volume, but different specific gravity, are dropped simultaneously from
the same height into water, the greater weight will settle on the bottom
of the vessel or tank first.
This result is attained by the jigger through a series of rising and
falling movements. The ore must be sized for successful jigging, from
aV to J of an inch in size. Ore that is too coarse requires too much
power, and when it is too fine it has a tendency to pack.
The simplest form of jigger is an ordinary sieve having a perforated
wire or metal bottom. This is shaken or jerked up and down by means
of a frame and lever in a trough of water; the sand and gravel being
thrown to the surface is removed by a scraper.
This form of machine is still employed on some of the Cornish
mines, and is useful in prospecting operations.
The modern form is the automatic three-compartment jigger with a
lever motion. The pulsation is got by the reciprocating action of
the piston or plunger. The heavy ore passes into the bottom of the
hutch in the jigger, from which it can be emptied through a plug valve
into the receptacle below.
.206 TIN DEPOSITS OF THE WORLD.
In Cornwall the majority of the mines pass the pulp directly on to
Frue vanners and classify the tailings for subsequent slime treatment.
In working this vanner care must be taken to ascertain by direct experi-
ment on the ore to be treated, the relative amount of water and pulp to
be supplied to the machine to get the best results ; the exact speed and
inclination required ; aH these points vary considerably with the ore
that is concentrated.
The average inclination is from 3 to 5 inches in 12 feet. That can
be increased if necessary to 10 inches or diminished to J an inch. The
average speed of the belt is about 32 inches per minute.
A good general plan in erecting a new machine is to set the frame
with a fall of 4 inches in 12 feet, and run about a speed of 200 revolu-
tions to the minute ; be sure that a good supply of fresh water is
readily available, run the machine for about an hour, and carefully
examine the concentrates.
If a sticky bed is formed on the belt, increase the grade a little,
but if there is no bed on a thin stream of pulp and water the grade
should be flattened till the right consistency of pulp is obtained. Of
the two extremes an insufficient bed is better than one that is too
heavy and sticky. About three machines to every ten stamps will be
found sufficient.
The WiLFLEY Table is coming greatly into use in place of
the huddle. This table should be started with but little pace
towards the waste-discharge side, and a thin sheet of water should
cover evenly the entire table, except that immediately below the feed
opening. When the feed is turned on the table will then be entirely
and evenly covered. It is important not to bow the surface of the table ;
and not to have any vibration arising from defective setting on the foun-
dations. The fundamental idea of the table is to wash away any small
particles of silica. From the time the pulp first reaches the table until
the concentrates drop into the box, the silica on the surface of the
pulp should be constantly washing towards the waste launder in a thin
sheet of water.
When the concentrates begin to come off the end of the table, the
side of the table is raised or lowered until the pulp separates at the
lower tail corner, the concentrates going to the concentrates box, while
the middlings pass into the middlings return trough ; the springs should
be run as loosely as possible. The movement is adjusted for a stroke
of f inch ; this has been found usually to give the best results, and in
no case should the stroke exceed 1 inch in length, nor should it be
made shorter than f inch. The progressive motion given to the
concentrates is accomplished by the short turn at the forward end
of the stroke. By raising the adjustment block the turn is sharpened
and the throw greater. In lowering the block the throw is shortened
and the turn made less sharp.
Always allow ample time to elapse in which to note the results,
as the entire bed of concentrates on the table is to be moved before
a change becomes apparent. Assaying is the only sure method of
determining the character of the work performed by the table.
PL AH
FIG. 32.— CONCAVE BUDDLE.
TIN CRUSHING AND DRESSING MACHINERY. 207
The Buss Table. — The construction of this machine is simple, and
the adjustment to suit the class of work required easy. The general
precautions enumerated in the description of the previous concentrating
machines apply equally to this.
From these various methods of concentrations the pulp passes
to a system of convex and concave buddies. A great many mines in
Cornwall still use the old round convex type of huddle, which is of
extremely simple construction, the huddle being made in a circular
pit made in the ground of about 22 feet in diameter and about 1 J deep.
These buddies can be arranged so that the smaller ones treat the
richer slimes and the larger ones the poorer.
The sides of the huddle pit are made of concrete or bricks. The
floor of the huddle is set with an outward inclination of about 1 in
30. Smooth boards can be used, but concrete with a smooth surface
of pure cement is better. A revolving head is fixed to a shaft and
carries four arms, which distribute the slimes in an even layer. To
each of the four arms is attached a board which carries a cloth or
series of small brushes ; these sweeping round, smooth out each
successive layer of mineral as soon as formed. The number of
revolutions vary according to the mineral treated, al>out four a
minute being the usual rate of speed.
A small sluice gate in the outward rim carries away the waste
overflow. Holes are made in the door ruf the sluice gate, which are
plugged up as the layer of deposited mineral rises, till the deposit
equals the height of the cone, and presents the appearance of a level
surface. At this point the machine is stopped, rings are drawn round
the various concentrates formed, the rich concentrates are taken
out and re-buddled if necessary, or may be sent at once to the
dolly tub.
The disadvantaoes of this type of machine are, first, no finished
product can be made at once, and also all the handling must be done
by hand labour, also the machine must remain idle during the process
of clearing it up.
" Green's Vanning Table " for the concentration of slimes makes
an excellent substitute for the old-fashioned huddle ; it gives a
clean, rich concentrate with no handling of poor middlings. The
table has a flat surface fitted with longitudinal riffles of graduated
length ; and a motion is obtained resembling the action of vanning
by hand.
The Concave Buddie, — The circumference here is higher than the
centre where the discharge takes place. This buddle is generally used
to enrich the heads from the round buddle. The slope given to the
floor is about 1 in 12. The larger proportion of the ore is deposited near
the circumference of the floor, almost immediately under the circular
ledge; the waste waters flow over the top of the swing ring into a well
and then into the settling pits.
There have been many new slime tables invented and used. The
author saw a concentrating slime table in use on the Dolcoath Mine,
known as the Acme combined concentrating table ; the advantages
208 TIN DEPOSITS OP THE WORLD.
claimed for this form of table are as follows : 1st. The pulp by this
frame is doubly treated automatically. 2nd. The frame requires little
attention when once adjusted. 3rd. There are no middlings. 4th. It
requires only half of a horse-power to drive it. /)th. Will make a
cleaner and more valuable concentrate than other machines of a similar
nature. On the whole this seems to be a fairly satisfactory machine^
and certainly presents a few small improvements to the ordinary
revolving slime table.
What is known as the revolving slime table is a circular conical
table about 18 feet in diameter. The ore is fed on the outer edge in a
small stream with water flowing down the incline to the inner edge,
the heavier particles being deposited, which adhere to the table ; the
revolution of the table carries round the deposited material, which is
subjected to the washing action of clear water flowing over it, and is
eventually brushed and washed off* the table, the clean concentrates
dropping into launders placed below to receive them ; the table thus
continually arrives cleaned to receive the flow of ,pulp, being freed
of waste, middlings, and clean concentrates before the full revolution
is completed.
The surface is made of wood, carefully dressed — but in the
author's opinion a far better wearing surface is obtained by cement,
coated with a mixture of 25 per cent, turpentine and 75 per cent,
coal tar, laid on with a brush, when the cement is sufficiently dry to
absorb it. This face will keep in good working order for two years,
whilst the wood has a tendency to work into grooves, and thus tin ore
is lost.
The Evans slime table is also used, and this machine can be kept
constantly at work without loss of time in cleaning up. The pulp is
delivered into the centre of the table, and the rich concentrates are
washed off by a slow jet of clean water. It has capacity for treating
about 25 tons a day of 24 hours. The chief disadvantage of this type
of table is the difficulty in obtaining anything like a perfectly even
motion. This trouble is largely overcome at Dolcoath by using a worm
and pinion, the table being driven by an electric motor.
The Linkenbach table possesses many advantages ; the initial cost
is, however, very high, and it is not in general use on that account.
In order to obtain the highest extraction possible from the slimes it
is necessary to re-grind a portion of the coarser material. Various
machines have been used for this purpose. At the Mount Bischoff*
Tin Mine a Chilian mill is used for this purpose, but it is an inefficient
grinding machine, and not so well suited as the improved tube mill or
barrel pulverizer in use in Cornwall.
It is believed to be the earliest form of the present tube mill now so
largely used in gold slime reductions.
It is an exceedingly simple machine to work. There are no screens,
there being free exit for the ground pulp. It requires about 6 h.-p. to
drive it. Scrap-iron or flints may be used in the barrel for grinding.
A machine 4 feet in diameter, 12 feet long, has a grinding capacity of
15 tons every 24 hours, making 40 revolutions per minute.
P CAN
et.C V ATI ON
PIG. 33.— SLIME TABLa
TIN CRUSHING AND DRESSING MACHINERY. 209
A subsequent treatment of the pulverized slimes is made over
slime tables as described. Automatic rag frames and settling pits are
then used, in order to concentrate the rich slimes and leave the waste
as poor as possible ; the operation may be profitably repeated several
times, as tin ore is very difficult to separate from its gangues when
in a fine state of division.
The separation of wolfram from tin ore has been in the past a
problem of considerable moment to the tin dresser ; but thanks to the
development of the magnetic separator, what was once a source of
loss and trouble has been turned into a product of considerable
value.
In magnetic dressing there is no universal machine that can be used
for all purposes, and the separation of wolfram from tin ore can be
effected by either a dry or wet separation. The machine that has been
used with success in Cornwall in the Glitters and other tin mines is
the Wetherill separator, cross-band type (1. C. 4.), the best type for the
separation of wolfram from tin.
This machine takes about 1^ h.-p., and makes a remarkably clean
separation. It is of simple construction and easily manipulated.
In considering the most successful methods of modern tin-dressing,
the best known systems are those in which, first, tin-dressing with
classification and the use of some form of concentrating table ; second,
tin-dressing is carried on without classification, by means of Frue
vanners.
Unless two small testing plants could be arranged so as to run side
by side, treating the same class of ore, with the object of proving the
relative value of these two systems, it will be impossible to settle
definitely this vexed question.
But in the writer's opinion, the better system is that of first classify-
ing as closely as possible by means of up-current classifiers, so as to
carry off the finer slimes, and to leave the coarser product to be treated
by impact screens, before passing on to some form of concentrating table
like the Wilfley, Buss, or Green. The resulting products from the
tables are : first, a clean concentrate ; secondly, a middle product ; and,
thirdly, waste.
I do not believe in returning this middle product on to the table.
From careful microscopic examinations of this middle product, it is
shown that the majority of the tin in it, is adhering to very small par-
ticles of gangue, and it is necessary, in order to recover the cassiterite,
to pulverise this middle product, and no amount of returning to the
table without re-grinding will effect any considerable saving. This
middle product should be run direct into some form of pulveriser, like
the ordinary tube or ball mill. For this system the Frue vanner is
impracticable, for although the concentrate is clean, there is no middle
product, while the so-called waste contains a considerable percentage
of tin, which necessitates a further handling of the whole of the
tailings, in order to recover the tin ; and generally the series of
operations dealing with these tailings commences with some form of
classifier.
210 TIN DEPOSITS OF THE WORLD.
The only case where it might be better to .instal Frue vanners is in
a small mine where first cost is a matter of great consideration, and
where fine working is not a matter of moment.
After the preliminary treatment in either of these systems comes the
the great question of the successful recovery of tin slimes. The product
from the classifiers, as well as pulverisers, flows into spitzlutten, and
here the slimes and fine sands are readily separable from each other.
Another way is to allow the products to flow into a modified form of
slime pits, used alternately, with an outlet at the lower end which can
be progressively closed by a series of stops. The following is the general
method of procedure : — To fill the pit the stops are taken out, and the
stream of fine sand and slime accumulates in the upper end ; the fine
sands settle readily, while the slimes flow continuously either direct on
to slime tables, or first over dead frames into small pits, before passing
over the slime tables. As these sands begin to accumulate in the pit,
the stops are put in at the lower end. These do not interfere with the
outflow of the slimes, but merely assist at keeping back the sands in the
pit until fulL These sands can be readily concentrated on some form of
slime-treating table. In my opinion, a Speery vanner is an excellent
machine for this purpose ; but no difficulty will be experienced if the
ordinary huddle form of concentration is used.
It would be as well at this point to try and arrive, if possible, at a
working definition of what slime really is. It is the common practice
among miners to class everything that passes through a ISO-mesh screen
as slime, but that hardly conveys the right impression of the form of
slime that gives trouble to the tin dresser. It might be defined as
follows : — " When the slime remains suspended in clear water for a
perceptible time, or that it will sink at an average given rate of one inch
in twelve seconds, and that when rubbed between the fingers no gritti-
ness is felt." The measurement of these particles is a practical
impossibility, as they would require to be measured to the ten-thou-
sandth part of an inch. It is also quite true that the water with this
form of slime in suspension, will also carry away the fine sands ;
but as I have already explained, these sands do not present the
difficulty.
From my experience in Cornwall, the question of the treatment of
these fine slimes has not received the attention that it merits, and the
only place where this problem has been tackled on a large scale is at
the Mount- Bischoff* Mine in Tasmania. Here they have a very exten-
sive series of slime pits, where the slimes are given space and time to
settle, both being necessary to eflect a complete precipitation.
At the Glitters Mine, of which a description is given, this form of
slime is not treated ; and in the Camborne District its recovery is
undertaken by separate tin stream companies on the Red River with
more or less success.
Another question over which there has been a controversy is the
question of a graduated form of crushing. There are mines that can be
successfully worked by fine crushing ; but I think there is little doubt
that if a hard ore is sufficiently pulverised to pass through a 40-me8h
TIN CRUSHING AND DRESSING MACHINERY. 211
screen that it will found to contain a considerable percentage of very
fine slimes ; whereas, this same ore crushed through a 25-mesh and then
classified and pulverized, the residue will be found to contain a far less
percentage of slime.
Of course the question of first cost is a matter of serious importance,
as it is considerably higher when the system of graduated crushing is
adopted.
As these questions are still undecided, 1 have thought it better to
give in this chapter a complete synopsis of both the systems, as I find
that there are many capable engineers who hold strong views on both
sides, and it is only by actual experience, or ascertained results on
the particular ore to be treated, that a definite conclusion can be
arrived at.
Where the loss on the average lode matter is only 3 lbs. to
the ton, the tin dresser is justified in regarding his operations as
successful.
The Treatment op Tin-Wolfram-Copper Ores at the
Glitters United Mines.*
The new Glitters mill, as originally erected, was divided into two
separate systems, one for the treatment of tin ores containing little
wolfram, and one for tin ores containing a large percentage of wolfram ;
but owing to the successful working of the magnetic separation the two
systems have to great advantage since been merged into one.
The arrangement of the mill is now as follows : The greater part of
the ore arrives at the back of the mill and passes over two grizzleys,
whose bars are 2 inches apart, the fines falling directly into the large
storage hopper, whilst the coarse pieces fall on the platform and froiii
thence are fed into a 15 in. X 10 in. Blake-Marsden rock-breaker,
and delivered also into the same storage hopper. The ore is then passed
by four Ghallenge feeders into the boxes of four batteries, each of five
stamps. The weight of each head is 800 lbs., and they are dropped
ninety -five times per minute. The pulp is passed through No. 25-mesh
gun-metal woven wire screening. The use of this material for the
screening is necessary, as the ore at times contains a considerable
amount of free acid, and gun-metal screening was found to last almost
twice as long as steel screening
A smaller portion of the ore is dumped into a storage hopper, and
is, after the elimination of its fines by the automatic shaking screen, fed
into a small 12 in. X 8 in. rock -breaker. The ore then passes
through a set of friction-driven rolls of 28 in. diam. x 12 in. face
and hoisted by the elevator to the vibro screen, from whence th« fines
are sent to a No. 6 ball mill, which crushes them through No. 30-mesh
* Trans. Inst. Min. and Met. F. Dietzsch, 1905.
O 2
212 TIN DEPOSITS OF THE WORLD.
screening. The coarse material collecting oh lop of the vibro screen
returns to the rolls and is re-crushed.
The combined pulp from the 25 stamps and the ball mill pass
through three spitzlutteu ; two of these have three compartments of
varying depths, and one has only two compartments. The product of
each spitzlutten passes to a Buss swinging table, while the overflow of
the three spitzlutten (fines) goes to a ten-compartment condensing and
classifying spitzkasten, 50 feet long by 6 feet wide on top, and
5 feet 6 inches deep. Three pairs of these spitzkasten compartments
supply their pulp through launders to three two-compartment distribut-
ing boxes, which in turn feed three double Luhrig vanners.
The remaining four spitzkasten compartments supply a double
vanner through a single two-compartment distributing box. The over-
flow at the end of the series of spitzkasten, together with the tailings
from the Buss tables, the overflow of the distributing boxes, and the
tailings of the Luhrig vanners outside of the mill, pass into a second
eight-compartment condensing spitzkasten 40 feet long, 6 feet wide on
top, and 5 feet 6 inches deep. While passing through the last-
mentioned spitzkasten, a small quantity of lime in solution is added,
which clarities the water sufficiently to enable it to be pumped
back by a centrifugal pump to a water tank and used again in the
battery.
The Buss swinging tables, to which reference has been made, are
eight in number, and the heads from these pass forward as witts to the
calciner, whilst the middlings are at present returned to the tables by
elevator wheels, one of which is attached to each table. The tailings,
that form a large proportion of the whole pulp charge, go direct to the
waste heaps. Experience has shown that the return of the middlings
to the table is not the correct procedure, as a large proportion of coarser
particles tend to circulate continually, unless they are cut off* by means
of a piece of wire screening.
In future it is intended to collect the middlings from the tables and
to re-crush them in a wet ball mill, that is at present being used to
re-crush a stock of high-grade middlings, which had accumulated in
the past. After re-crushing, the table middlings, together with the
overflow of the spitzlutten, will be treated on the Liihrig vanners. At
the same time, by using a No. 20-mesh screen, the first crushing of the
ore will be made much coarser, and so decrease the production of slimes
and increase the tonnage treated. It may here be remarked that the
ball mill has been found to slime very ^uch less than the stamp mill,
and that even after re-crushing in a ball mill through an 80-mesh the
production of slimes was found to be comparatively small. It follows
that whilst the tables finally eliminate a very large proportion of the
light waste in one operation, and only allow waste particles carrying
some minerals to be caught as middlings, the quantity of these latter is
by no means large, and can be easily dealt with in a small ball mill, so
that as a net result not only is the advantage of not sliming the ore
attained in the first instance, but the capacity of the mill is greatly
increased by this form of graduated crushing.
TIN CRUSHING AND DRESSING MACHINERY. 213
Each of the five distributing boxes in front of the Liihrig vanners
has two compartments, each of which supplies one-half of a double
vanner. Four of these boxes take the original pulp from the large
spitzkasten, whilst the fifth takes the middlings from the other four
vanners, so as to allow of a separate re-treatment of the middlings.
The middlings from the vanners are collected and pumped by a centri-
fugal pump to a small condensing spitzkasten to remove the surplus
water, and the bottom discharge of this spitzkasten passes to a distribut-
ing box from which each compartment feeds one-half of a double vanner.
Formerly these middlings were allowed to mix again with the general
pulp without being re-classified, but as a large proportion of them was
found to circulate without being further concentrated, they are now
practically treated on separate vanners under appropriate conditions for
their concentration. The heads from the vanners are a high-grade con-
centrate, and go to the calciner, where they are roasted separately from
the coarser concentrates of the Buss tables. This arrangement has
been found to save some re-classifying of the roasted concentrates, and
secures a better market for the coarse products.
The concentrates from the Buss tables are usually free from any
siliceous waste, and contain only the sulphides of iron, copper, and
arsenic, the oxides of tin and wolframite. They are of a very much
higher grade of concentration than the average Cornish concentrates
cabled " witts," and are separately roasted and then electro-magnetically
treated. The vanner concentrates, which contain much of the iron
oxides originally in the ore, are of lower grade as compared with those
from the Buss tables, and are therefore, prior to their electro-magnetic
treatment, re-classified and enriched in ordinary convex Cornish
buddies, in which the bulk of the iron oxides are removed and go to
waste.
The magnetic separator used at Clitters is the Wetherill machine
known by the makers as the '* cross-belt type." It consists of a wooden
frame carrying two pairs of electro-magnets in juxtaposition. Two
magnets are beneath the main conveying-belt and two above, and the
winding is arranged in such a manner that the north pole of one magnet
is opposite the south pole of the other. The poles of the lower magnets
are flat, while those of the uppa magnets are pointed. In this way
four long, narrow, and highly concentrated fields are formed, through
which the main endless conveying belt passes. The ore is placed in a
hopper, and by a distributor is evenly spread on the main conveying-
belt. As soon as the ore enters the magnetic field the magnetic portions
fly to the upper poles, which, being pointed in shape, have a greater
attractive power than the flat lower poles. The lines of magnetic force
converge to the pointed poles, thus making the field in their proximity
more concentrated. Smaller endless carrying belts pass underneath the
upper pointed poles, i.e. between the main conveying belt (with its
charge of mineral) and the poles, and these small belts run in a
direction at right angles to that in which the main conveying belt
moves.
214 . TIN DEPOSITS OF THE WORLD.
The magnetic particles flying towards the upper poles are intercepted
by the small carrying belts, and by adhering to the lower surface are
carried sideways out of the magnetic field, so that they cease to adhere
to the belts and drop by gravity into separate receptacles. The dis-
tances between the upper and lower poles can be regulated by set
screws, and in this manner the intensity of the field can be either increased
Or decreased.
The intensity of the field can be further regulated to a nicer degree by
means of a rheostat, which regulates the current round each pair of magnets.
The first pair of magnets are arranged so as to give a weaker field than the
second pair, and in this way the strongly magnetic particles are removed
during the passage through the first two fields, whilst the weakly mag-
netic substances are removed in the last two fields.
The first field removes the greater portion of the magnetic oxide of
iron, and the product from the second field consists principally of the
other oxides of iron with oxides of copper adhering. The third field
yields some more oxides of iron mixed with wolframite, and the fourth
field produces fairly clean wolframite. The non-magnetic product fall-
ing off the end of the main conveying belt consists of the oxides of tin
and any siliceous waste that may have escaped elimination in the wet-
dressing operations.
The product from the first magnetic field, provided that the field
be kept sufficiently weak, is generally sufficiently poor in tin, wolfram,
and copper to be allowed to go to waste. That of the second field, if
sufficiently free from tin and wolfram, is sold to the copper smelter and
fetches a good price, owing to the high percentage of the oxides of iron
present. It also frequently contains up to 10% of copper.
Sometimes the products from the first and second magnetic fields
have too much tin and wolfram adhering to the oxides of iron and cop-
per to admit of the usual course being followed. If this is the case
these products are re-treated after having been further crushed in the
dry state in the No. 2 ball mill. This is only done after a sufficient
quantity has been allowed to accumulate to make it expedient to dry
the ball mill for that purpose ; for these products, having once been
roasted, will contain too much acid to be crushed with impunity in the
wet way.
The coarse products from the table concentrates obtained from
the third and fourth fields, consisting of wolframite mixed with some
oxides of iron, are usually clean enough to be finished in tossing-
kieves.
The fine-grained products from the vanner concentrates obtained
from the third and fourth magnetic fields are first huddled and then
finished in kieves. The non-magnetic product is usually sufficiently
clean to be simply tossed in a kieve to make it marketable as tin
oxide.
L^ AJ. JLJl JO-, li,jL "« '^S?
"Hi**'--
X ^-
coNvc5t-^«ui
KiEvea
* PUMP
O
Are toatmd fpaeltmel i^mkinttnmd.
(Hea^fkir Market)
Fig. 34.— ORE-DRESSING PLANT OP THE GUNNISLAKE GLITTERS MINE.
(D. A. MACALISTER.)
TIN CRUSHING AND DRESSING MACHINERY.
215
Glitters United Mines.
Details of Milling and Dressing Costs for month of June, 1903.
No. of Stamps, 25. No. of days, 26. Tons emshed, 2,540.
Mill Coat.
Total Cost.
@ per Ton.
X. d.
£ ».
d.
d.
2-12 hr. shifts
2 Engine Drivers @. 4/2
\
II 11
per shift
2 Stokers @ 3/4 per
shift
216 8
173 4
\ 19 10
1-84
II II
2 Shift Foremen @ 6/-
per shift
312
3- 8 hr. shift...
3 Stamp-men @ 3/4
per shift
260
2-12 „ ...
2 Table Floor men
@ 3/4 per shift ...
173 4
II H
2 Vanner Floor men
@ 3/4 per shift
173 4
73 9
6-94
days only 10 hr.
3 General Helpers® 3/4
shift
per shift
260
Do.
1 General Helper ® 2/-
per shift
52
Do.
1 each Fitter and Smith
@ 5/- & 4/2 per shift
233 4
108 Tons of Coal® 17/-
per ton
...
91 16
8-67
Shoes and Dies
25
2-36
Screening Bronze Wire
(gun-metal in use no^)
...
5
0-47
Belting, Feeder Spares,
bearings, etc.
...
12
1-13
Oil
5 15
0-54
Waste, rivets, files and
sundries
1
1 15
11
0-17
Total Mill Costs ...
£234 5
11
1/10-12
Calcineb.
2 Shift-men @ 3/4 + overtime Sundays
196 8
9 16
8
0-93
12Ton8of Coal® 17/-
204
10 4
0-96
Magnetic Sepakatok.
2 Shift-men at 3/4 + overtime
9 16
8
0^3
Buddle Flooks.
3 Men and 18 Boys
45 6
2
4-28
Pumping.
2 Shift-men @ 3/4 per shift + overtime
for cleansing
...
10 4
9
i 3'B8
30 Tons Coal @ 17/-
...
25 10
2
^
Total Milling and Dressing Costs ...
£345 4
2/8-60
216 TIN DEPOSITS OF THE WORLD.
The existing system of tin dressing in Cornwall can only be
defended on the ground of being established, and involving * expense to
change to a better. Experiments have been made with a view of deter-
mining a better process by the adoption of modern machinery. In any
comparison of the existing and a proposed system, the following factors
have to be considered : —
1. The relative costs of operating.
2. The relative losses in metal,
3. The relative commercial value of the product or " headings."
Proper values have to be attached to each of these factors in a final
decision. It does not follow that the cheapest process to operate is
necessarily the best, since the loss in tailings or an increased cost of
treating products may more than neutralise the apparent advantage.
Neither does the smallest loss in tailings of itself indicate the best
process commercially, since it may involve higher cost of operating and
higher cost or losses in realising the products. It is, therefore, obvious
that any choice of methods must rest on a consideration of all three of
the factors named.
A. — Single Treatment without Classification.*
This method involving the smallest amount of machinery and least
attention would naturally commend itself for a first trial ; but it seems
probable, from the richness of much of the ore stamped, and the extreme
fineness of the tin in the battery pulp, that losses will be too high to make
it advisable to adopt so simple a treatment. There is no doubt that with
a proper number of vanners and avoidance of excess of battery water,
with steady speed of line shaft, and proper attendance, very close work
can be done on the average ore as crushed, and a good clean product
be obtained with comparatively poor tailings. It is, however, so easy
to insure somewhat better results and diminished loss by a re-treatment,
that it does not seem desirable to stop at the first step of improvement
over existing methods.
B. — Single Treatment with Classification.*
The question of classification is a much debated one, and chiefly
because circumstances alter cases so much. Those who hold that
classification is essential to close concentration have certainly not had
an opportunity of studying all the facts under varying conditions of
working.
Now the general custom is established to put the unsized pulp
direct on the Frue vanners, a custom thoroughly justified by the very
close and excellent concentration hereby resulting. There is no upsetting
of established laws in this on examination ; but the results depend on
* These notes were given to the author by Messrs. Fraser and Chalmers as the
result of an exhaustive series of experiments carried out on the Dolcoath tin mine.
TIN CRUSHING AND DRESSING MACHINERY. 217
a complicated series of elements, some of which are overlooked by those
who lay down fixed rules. Some of these elements may be referred to.
The argument for classification rests broadly on the fact that an
ore crushed through, say, a 40-mesh screen consists of all sizes of
particles (from what will just pass the holes down to impalpable dust
or slime), and that the largest sized grains of waste-rock cannot be
washed away from the finest particles of mineral without excessive loss
of the latter. The broad fact is true, but only under certain conditions
is it as important as it seems. On a fixed surface, or on a slowly
1 evolving surface (as in buddies), or on a bumping surface like a Rit-
tinger table or Bilharz table, the difference in sizes of particles tends to
neutralise differences of specific gravity, and the conditions of working
so as to get off* the larger particles of waste rock are unfavourable to
the close saving of slime mineral. Ou a rapidly shaking (not bumping)
surface, the conditions are not so unfavourable, as the larger particles
do not rest on the surface owing to its rapid motion, but remain, as it
were, suspended in the water, and can be moved down in its current
with much less force than in the previous cases. That this is no mere
theory is shown at once by the simple fact that a sixpence put flat on
any huddle or bumping table would pass at once into the headings,
while it will not do so on a Frue vanner, where it is unable to pass the
washing water jets. This indicates a difTerence in the conditions of
working in the two types of machines.
Some of the points in practice which become at times disadvan-
tageous in connection with classification are these : — The introduction
of clear water in the sizing boxes makes the overflowing fine slimes far
too thin for effective work on vanners, unless large pointed settling
boxes are again used to thicken the pulp by getting rid of excess water.
The slime mineral which constitutes the chief loss on the vanner or
other concentrator is that which goes off in the overflow from sizers.
The vanner will not do close work if a large quantity of water runs on
it ; the pulp flows down too rapidly to allow of the fine mineral settling
on the belt and so being saved. Of course, if this overflow from sizers
carrying the most difficult mineral to save is run off to waste, or settled
as a separate product, or treated on other machines, the vanners which
take the coarser sizes of pulp appear to be doing better work because
they are relieved of much of the slime mineral, and their tailings are
cleaner ; but in order to compare results with and without classification
the proportional value of the overflow pulp must be added to that of
the vanner tailings, for comparison with the average tailings value when
the whole pulp unsized is put over the machines. Again, it is estab-
lished that the vanner does excellent work on unsized pulp (not coarser
than 40-mesh), and that much of the very finest slime mineral is saved
when so operating ; that is, some of the concentrates are just as fine
as most of the slime mineral which constitutes the loss. The very
finest slime mineral will save on a Frue vanner if it settles on the belt
in flowing down its length, and what has failed to so settle and be
saved can to a great extent be caught by running over a second
machine. From this it follows that the loss of fine mineral from an
218 TIN DEPOSITS OF THE WORLD.
unsized pulp is not a necessary loss due to special difficulty in saving
that particular mineral, but is largely what may be called an accidental
loss ; the mineral has not happened to settle to the belt. A flood of
water lessens the chance of the settling, and increases the loss of fine
mineral in the tailings. When an unsized pulp is fed on the vanner a
bed of the coarser sizes is formed, and tbe water and fine slimes filter
and work down comparatively slowly through this bed, and not in
uninterrupted waves, as when fine slimes alone are fed on. It follows
from this that the fine slimes do actually, with an unsized pulp, have
rather a better chance of depositing the finest mineral on the belt
during the slow passage down the belt with the vanning or settling
motion imparted. To get good work out of fine slimes alone on a
vanner, not only must there be no excess of water, but it follows the
capacity of the machine becomes very small. The argument from the
above is that in many cases the proper method of increasing the effec-
tiveness is not by classification, but by double treatment ; that the
separation of the greater part of both coarse and fine mineral can be
satisfactorily effected on unsized pulp, and that the portion difficult to
save is not rendered more amenable by separation, but rather the
process is in a measure complicated by the introduction of excess of
water. It may be urged, and justly, that as the loss of mineral in the
tailings is practically all in the slimes, it seems unnecessary to re- treat
the whole mass of material. A most effective compromise of the pros,
and cons, of classification is here indicated. A simple and economically
vi orking arrangement of vanners direct on unsized pulp will effect a
very high saving of mineral as compared with any other form of machine,
and deliver good clean concentrates, without the disadvantage of excess
of water from classification. The loss in the tailings can be mostly
separated as an overflow from a classifier, and will make a small pro-
portion of the original to be re-treated on other vanners after pointed
boxes, or on revolving buddies. The slime mineral by this means gets
a double chance of being saved instead of a single one, as when it is
separated in sizers and treated by itself on a vanner or other machine,
it is a good principle to catch the fine mineral as far as possible at once
instead of first drowning it with water.
C. — Double Treatment on Two Sets of Vanners.
This has been already referred to in general terms. It may be
repeated that the loss in the tailings of a vanner on most ores is in a
form quite susceptible of being reduced by treatment on a second
machine. The vanner differs from all other concentrators in practice
in this, that it is expected to treat the most difficult ores in one opera-
tion, making clean headings without any middling product to be
re-worked. The very excellence of its work seems to have precluded
the idea, in most cases, of using it twice over. Owing to the bad effect
of excess of water, the best results are not obtained if the tailings of a
4-feet machine are put over another of the same size, because the clear
wash water of the first machine has diluted too much the pulp for
TIN CRUSHING AND DRESSING MACHINERY. 219
successful working on the same width of belt again ; t.e., liaving more
water, it needs to be spread out over a greater width to prevent too
rapid a current. From this it follows that the taijings of a 4-feet belt
should pass to a 6-feet belt, or, better still, to two 4-feet belts. Of
course, if ample pointed box capacity be introduced between the two
sets of machines, the necessity for increased belt area is not established ;
but if the first machines are followed by a second set to reduce losses,
very close work is not so essential on the former, and they can be
somewhat crowded as to capacity, making it then advisable to treat
more slowly for the finest mineral on the second row.
D. — Single Treatment by Vanners, with Re-treatment of
THE Slimes from Tailings on Revolving Buddles after
Classification.
By sizing the tailings of a single set of vanners, treating direct the
unsized battery pulp, it will be found that the slime portion will show
on vanning, by the shovel, a very perceptible head of tin. This slime
portion is practically a concentrated product of the average tailings,
containing as it does a large proportion of the whole of the tin escaping
the vanners. Being free of the coarser portion of the original pulp, it
is in a condition favourable for treatment on revolving buddies, which
are not so unfavourably aiFected by excess of water as the vanners,
owing to greater area. It may, therefore, be urged that, as either
settling boxes to get rid of excess of water must be used, or a relatively
large number of vanners be employed to handle the thin pulp, it is
better to employ a cheap machine like the revolving huddle, even with
its attendant disadvantage of middlings product. It is, of course, no
reflection on the work of the vanner that it should be followed by
another class of machine, as it is quite certain that if buddies were used
first, the vanner would show a large yield from their tailings and
middlings products. The question is merely one of expediency as to
handling a sized and partially concentrated portion of tailings. For the
first treatment of the pulp there can be no question as to the advantages
of the vanner over any form of huddle. Even on the special tailings
product it is probable that, by a thickening of pulp or division over a
sufiicient number of machines, the vanners would make cleaner headings
with less loss in final tailings than two rows of revolving buddies, the
lower treating the middlings of the upper ; but with either arrangement
the loss will be so small that it can safely be ignored when considered
as tonnage on the original ore crushed.
An advantage connected with the sizing of the vanner tailings is
that a special size of the coarsest particles of the crushed ore can be
delivered as a product for re-grinding in pulverizers, if found to contain
by assay sufficient metal to justify further reduction in size to liberate
it. This re-ground product would be elevated and pass continuously
over one or more special vanners added to the first row of machines ;
and the tailings of these join the general vanner tailings for classi-
fication before the buddies, or second set of vanners. In this way the
220 TIN DEPOSITS OF THE WORLD.
whole plant would be continuous -work in o^ and automatic, requiring the
minimum of labour and attention, and giving high-grade concentrates at
everj point.
The Relative Commercial Value of the Product or
" Headings."
At the present time the headings of the various dressing departments
are calcined and then re-dressed. There is no necessity for calcining
except to bring up the grade of product sent to smelter, and to diminish
smelting charges bj getting rid of sulphur and arsenic compounds
present. On the contrary, there is a very decided objection to the cost
of calcining ; and equally to the labour and loss of tin in re-dressing
the calcined material.
The products from the old fixed buddies are certainly not as clean
as the concentrations would be from a system of modern dressing as
already outlined, and an economy is here certain in the final process.
It is absolutely certain that the cost alone of calcining would be a
margin saved as against a somewhat increased cost of smelting ; and
even assuming that smelters would themselves calcine such a product
before smelting, the question of relative cost would simply be as
between doing this at the mine or at the smelter's. If still done at the
mine there would at least be no increase over existing cost, and the
question of re-dressing can therefore be independently considered. The
re-dressing of the calcined headings involves an unavoidable loss of tin.
After the greatest care in trying to save all the slime tin possible, it is
now again put in water and over a variety of machines, handled and
re-handled with a positive loss of a percentage of what has already
with great trouble been obtained. The cost of this re-dressing has also
to be considered ; and when this cost is added to the direct loss, there
is clearly a very good margin of profit to set against a little increased
cost of smelting. In considering this modification it must not be for-
gotten that, when applied to really clean concentrates, such as it is
proposed to make in the first place, the result is very different indeed to
what it would be to compare simply costs of smelting present
" headings " raw as against present calcined and re-dressed mineral.
In the discussion on the paper read by Mr. Sydney Fawns, " Notes
on the Mount Bischofi^ Tin Mine," Mr. H. M. Morgans contributed the
following remarks to the Institution of Mining and Metallurgy, 19th
January, 1905 : —
" Referring further to my offer at the last meeting, I have now ob-
tained permission from Mr. R. Arthur Thomas, the manager of Dolcoath
Mine, and from Mr. A. Mount-Haes, the Humboldt Company's re-
presentative, to make use of the results of the tests which the latter
company carried out on about 9J tons of Dolcoath ore. I have no
information as to the part of the mine from which the ore came, but it
is probable that for such a test the ore chosen was of ordinary average
quality, representing a fair sample of the mine produce.
" The accompanying diagram shows, in perhaps the most concise way,
the operations through which the ore passed. The percentage weights
TIN CRUSHING AND DRESSING MACHINERY.
221
sp
g^
**3
§5
^ty
^ %^ rTcUlings J9So%-to waste.
1 5 § \BlackTmrgimlUy.0ii5%,nmshedpwdu^ ,
I
o
o
Tailing 20 23% to waste .
Midd&nffsOl4%to be retreated in pmctice.
Slackliii1^gualjify064%,nnishedprodj^
o
^^Tailings/477% towaste.
^<^\^ -Middlings 062% to be retreated uipnzcUce
ii 5 \^£lajcklini*^guualily 046%, finished product .
^
Tailings 2S^6% to waste .
.Middlings934%-Bg^t^iny
-Bla£klui,2'!fgttamy. 0//%possidtgror \
regrimlmg.)
-BlackTm, /^^ gualitj/ / 25% finished p/vdiuU,
222 TIN DEPOSITS OF THE WORLD.
given refer to the total dry weight of crude ore. The diagram is self-
explanatory, and the only comments I will make on it aro, first, that the
screens of the stamp mill were no finer than 28-mesh, after which the
proportion of ore which needed further crushing in order to ohtain a
good extraction was about 10'o%; and, second, that with this com-
paratively coarse crushing, 40'o6% of the crude ore was treated by
simple jigging, 31*22% being obtained from the jig as finished products,
of which l*2o% and 0*11% were first and second quality black tin
respectively, and 29*86% were tailings.
" As regards the assay value of the various products, I give the
following figures, which I understand were obtained by the process of
vanning at Dolcoath. The Humboldt Company say of these figures
that their chemical assays, of which I have no copy, agreed in the case
of the concentrates, but differed in the cases of the crude ore and tailings,
and they take no responsibility for the values : —
Tin Oxide.
Crude ore - - - 100 00% - - - - 2*00%
1st quality concentrates 2*7 % - average assay 80*00%
2nd „ „ 0*11% - „ „ 48*5 %
Middlings - - - 1*21% (to be re-treated)
Tailings - - about 96*00% - - trace to 0*3 %
" Obviously the concentrates are shown to contain more tin oxide than
the crude ore. To clear up the mistake I am endeavouring to obtain
the Humboldt Company's own assay results, but my remarks at the last
meeting in reference to the fineness of Cornish ore are, I think, borne
out by the figures given above, and are not seriously affected by the
assay discrepancy."
( 223 )
CHAPTER XVIII.
DREDGING FOR TIN.
The process of dredging for tin in different parts of the world is now
so extensively practised, and so profitable, that it has reached the
dignity of an industry. Before describing the various types of dredges
at present in use, it may be as well to say a few words on prospecting
alluvial tin-bearing deposits.
Whether or not a piece of ground is suitable for dredging is deter-
mined by physical conditions. The alluvial ore deposit must be of a
considerable extent where the drainage area has been large. The best
deposits are generally where the rivers have opened into flats ; the
payable ore must be disseminated over a wide area, as a considerable
scope of ground is necessary for dredging operations. It is impossible
to dredge profitably very narrow portions of a river, especially where
there are large boulders. When the bedrock is hard, and the best wash
is lying on that bedrock, the tin-recovery of the dredge is materially
reduced. A piece of ground which fulfils the above conditions will bear
investigation. Great care must be taken in prospecting, not only in the
work itself, but also in placing the holes, and particularly in drawing
conclusions from the results obtained. The author can cite a case which
came under his notice on the Ringarooma River, Tasmania, where a
dredge was erected without a proper investigation of the depth of wash
and delivery of the tailings. The consequence was that when the dredge
was put to work it was found to be totally unfitted for the task it had
to perform, and the company lost all its capital ; this, unfortunately, is
only one out of many instances where want of careful investigation has
resulted in loss.*
What might be termed an ideal dredging area would be one that
could be successfully worked by the simplest class of plant, viz., the
sluice box type of dredge, and which displays the following features : —
(1) A long length of area, free from rocky bars, and of fair width.
(2) A good water supply.
(3) A loose, shingle wash, free from cement or clay .
(4) The absence of large boulders or sunken timber.
(5) The bottom or bedrock being soft and easily worked by the
buckets.
(6) The ground not being too deep, and all below water (an average
of 20 ft. is a good dredging depth).
* Trans. Inst. Min. and Met. E. S. and G. N. Marks, 1896.
224 TIN DEPOSITS OF THE WOKLD.
It is considered better to find a little gold all through the material
to Ije dredged, when examining an area, than to have it all on the bot-
tom, as the former condition will give steadier yields.
As one seldom finds ideal areas, it is a question, when inspecting
dredging ground, of deciding if it is possible to get over difl&culties
arising from poor facilities, or conditions, in the way of successful
operations. In judging these matters no arbitrary rule can be laid down,
but one must be guided largely by experience and knowledge of what a
dredge can do.
A good-sized area is necessary to give sufficient life to the enterprise,
as under favourable circumstances, with a dredge of 4J cub. ft. bucket
capacity, on the average, an acre a month would be worked ; this, of
course, depending on the depth to bedrock and the class of material to
be treated.
Bars of rocks across an area to be dredged, and over which the dredge
must pass, are not uncommon. When this is the case, there must be
facilities for dam building in order to float the dredge over the obstacle.
If the expense is not too great, blasting may at times be resorted to.
To do good work, a dredge requires a wide face to operate upon ;
narrow ground necessitates much shifting of lines, and entails loss of
time through having to take out corners. A dredge cannot work in a
paddock narrower than its length, as there must be sufficient room to
allow it to swing right round.
The depth of ground above and below water-level, and the class of
material that has to be lifted, must be considered, as the design of plant
depends largely on these factors.
As a general statement dredging ground can be classed as that in
which one finds, first, from grass roots to bedrock, one mass of stony
gravel wash, and second, a layer of wash on the bottom over which may
lie sand, or very light drift, or alternate beds of clay, sand, black soil,
loam, etc.
In the first case, when one only has a gravel or wash to deal with, if
the bedrock is soft and there is an efficient water supply available, the
proposition offers no difficulties ; but when there are other materials to
be dealt with such as are above enumerated, it becomes a matter of study
as to whether they can be successfully handled.
The objection to dealing with clay in thick beds is, that it is very
slow working when the buckets are filled with it ; it is frequently found
that they will revolve without emptying, and when they do empty, it is
in compact, bucket-shaped masses, which are apt to pile up on the drop
plate, where there is not sufficient water to carry them away, and the
buckets have to be stopped, the accumulation cut up by hand, and
washed away in small pieces.
A clayey adhesive wash is detrimental for the reason that there is
not time for it to be washed clean and the tin liberated, either by
treatment in a sluice run or revolving screen. Such classes of wash
require puddling, a process too slow for the treatment of the quantity
of material raised by a dredge. However, ground containing clayey
DREDGING FOR TIN. . . 22o
wash and clay over-burden is made to pay where it is rich in tin ore, but
the percentage won is small.
Bands of cement of any thickness are practically prohibitive for
dredging, although we have experience of one case where a dredge
worked ground 35 ft. deep in which there was a band of very hard
cement lying some distance below the surface, with free wash above
and below it. The wash was dredged below the cement, which remained
protruding from the face, after which the ladder was raised and the
buckets kept tearing at the cement, and in time it was broken up, but
at great cost of wear and tear, as buckets were destroyed continually
and links and pins broken. The area was, we believe, rich, but it is
very doubtful if this class of ground paid to work. Figures of working
costs are not obtainable, and we are inclined to believe that all profit,
over and above actual working expenses, would be absorbed by renewals
to plant, which were frequent.
Sand occurring in thick beds is difficult at times to deal with, unless
special means are adopted by the use of the sand elevator as described.
This only applies to paddock dredging where the tailings have no get-
away, as in the case of a river.
The presence of large boulders and loose masses of rocks do not
necessarily hinder operations, unless they occur in nests or patches,
under which circumstances the ground may be passed over without
working the bottom, floating room only being taken by the dredge.
Sunken logs and trees in the ground, if they do not occur in too
great an abundance, are not a bar to successful operations, but then
special means have to be provided for dealing with them in the shape
of a mast and derrick for raising the logs. We have had to deal with
trees 60 ft. in length, with 5 ft. butts, lying 15 to 20 ft. below the
surface.
The bedrock or bottom on which the buckets work must be soft to
insure best yields, for while the plant is at work the bulk of the tin
puddles down, and if the buckets cannot scrape the bottom there is great
loss.
In a country where the rivers and creeks are dry or nearly so in sum-
mer time, the question of obtaining sufficient water is often of moment*
As can well be understood, the more water available the better, but it
requires very little added water to keep going when a dredge paddock
is full, sufficient only to replenish soakage through the drifts and loss
by evaporation being necessary.
At times there is no available^water running on an area, in which case
a supply may be obtained from the surrounding country by gravitation.
There are cases where a flat above a river level has been worked, the
water supply being obtained by pumping. This was done by the
author in one case, using a No. 7 pulsometer, pumping water up 20 ft.
to the paddock. A supply of 120,000 gals, in the 24 hours was found
sufficient.
Although one can work with a very limited supply of water, there is
always the drawback that the water in the paddock becomes dirty and
thick, and this may cause loss.
"226 TIN DEPOSITS OF THE WORLD.
To determine dredging facilities, the foregoing conditions have been
pointed out as a guide as to where difficulties may be found, but
they may or may not, according to circumstances, be overcome, and the
statements are not to be taken as conclusive in any case, without a
practical test being made.
Having satisfied one's self that the local conditions and class of ground
to be dredged are satisfactory, the matter of tin contents should then
be studied and ascertained.
It is a difficult matter without going to great expense to get at the
(ictual average value of dredging areas. One must be guided by ex-
perience in judging prospecting results before deciding to equip any area.
Prospecting work is generally done with a boring machine, which
sinks a hole up to 6 inches in diameter. The test by a bore is nearly
as accurate as the test by shaft so far as the values obtained from the
gravel prospected is concerned ; but careful expert judgment must be
used to reach an approximately accurate conclusion from the result of
either bore or shaft. The more holes sunk the nearer you come to the
true value of a property. '* My deduction from a great number of cases
in actual practice," says Mr. W. A. Griffin, a well-known Californian
authority on dredging, " is that a dredge will produce from 60 to 70 per
cent, of the arithmetical average value shown by drill-holes when the
holes are placed approximately 5 to each 10 acres of ground." But, in
fact, it is much safer to bore at least one hole for every acre. A plan
that has been adopted as the result of practical experience is as follows : —
If the banks of a creek or river are being prospected, a line of holes are
sunk from 80 to 100 ft. apart, this is found where done with a 5 in.
auger to give a very fair average sample. The cost of this method of
sampling, under ordinary conditions, runs out at about Is. 6d. per foot,
from three to four holes per 24 hours 10 ft. deep can be bored by skilled
workmen. Dredging is carried on in the rivers as well as on the
banks contiguous thereto. In paddock -dredging a spit is dug inland
and the hull of the dredge is floated in it. Very little water is required
to float the dredge, and a small clear running supply to work it, as the
water which is pumped for washing purposes comes back to the pit.
The amount of water is determined by the cleanness of the gravel.
There are two factors which must not be overlooked in starting
dredging operations, viz., transportation and power, for where these are
high the average value of the property must be proportionately high.
Finally, it must never be forgotten that the " essence of the contract "
when prospecting for alluvial is to ascertain the exact depth of the
wash and water-level with a view to estimating the distance and height
that it will be necessary to deliver the tailings, and selecting the kind
of machine most suitable for the class of country to be treated.
There may be said to be five types of dredges that can be used : —
(1) The old Spoon or Dipper Dredge^ which at the best is an un-
satisfactory machine, and not adapted for work on a large scale, being
only useful for preliminary operations when prospecting. The chief
objection to this dredge is that it deposits the material intermittently,
and is both slow and costly in operation. However, as this machine
DREDGING FOR TIN. 227
has almost fallen into disuse, it is not necessary to say any more
concerning it.
(2) The Suction Type of Dredge. — This lifts up by means of a large
centrifugal pump the sands or gravels to be treated ; it can also raise
stones or small boulders provided they are within 2 inches of the
diameter of the suction-pipe without interfering with the proper
working of the pump or causing any injury to* the same. The suction-
pipe can also be raised or lowered as occasion requires ; this makes the
recovery of this type of dredge very effective, and enables it to work
round large masses of rock which would prevent the effective action of
the bucket type of dredge.
The mechanical drawback to the suction dredge is that a large pro-
portion of the power is used in pumping water, the proportion of wash
raised to water in height being relatively small, but the water raised can,
however, be used for sluicing purposes.
The New Wylie Creek Dredging Co., N.S.W.,is using a modern type
of ladder bucket dredge, the construction of which cost about £7,000.
The pontoon is 40 ft. in length and 20 ft. across. The machinery is
driven by a 12-h.p. compound high pressure steam engine. There are
27 buckets used having a capacity of 4 cub. ft., the average depth of
ground dredged is 20 ft. About 8,000 to 9,000 tons of alluvial drift
is treated per 24 hours, from this some 7 cwt. of Tin Concentrates is
saved, which when cleaned up give an almost fine sample of cassiterite
worth 76% of metallic tin.
(3) The Centrifugal Pump Dredge operates in a somewhat similar
way, except that the pontoon is resting on the bedrock, and the pump
operates from a well into which the gravels are washed by means of
hydraulic nozzles (from water supplied by small centrifugal pumps on
the pontoon), first into small sluices from the faces which convey the
gravels, and secondly into a main sluice leading to the well in which the
pump operates. When it is necessary to move the dredge, water is let
into the enclosure, and the dredge floated into the new position chosen
and the operation repeated. The tin-ore is saved by means of a long
sluice, as seen in the accompanying view of the Cope's Creek Company
centrifugal pump dredge.
The following is the machinery required for a suction dredge fitted
with hydraulic pumps and sluice boxes. The steam engine generally
in use is a coupled compound surface condensing one, with high and
low pressure cylinders working at a pressure of up to 150 lbs. to the
square inch, the steam being supplied by suitable boilers, and the
condenser has to be of sufficient capacity, so that the sluicing water
can pass through the tubes, thus avoiding the necessity for a circulating
pump. The pontoon is always built of well-seasoned timber, the
joints thoroughly calked, and the whole covered with two coats of
tar. A house is built all over this pontoon. The gravel pump to
raise the material is a large centrifugal pump, of which there are
several patent ones in the market differing slightly in construction. It
has a very strong outer case of cast iron. The pump shaft bearing ia
fitted with adjustable gun-metal steps, and it is necessary to provide
p 2
228 TIN DEPOSITS OF THE WORLD.
means to prevent the gritty water from the pump getting into the
bearings.
The hydraulicing water pump, the outer casing of which is better cast
in one piece, and is fitted with doors on both sides to give access to the
runner. An electric light plant must be capable of running the neces-
sary incandescent lamps on the pontoon, and four arc lamps for use
outside when working at night. Two nozzles are used for breaking
down the alluvial wash and debris. The width of the sluice box i&
determined by the amount of the materials and water delivered by
the gravel pump. The correct length and pitch of the sluice can only
be decided after direct experiment with the special class of alluvial
wash to be handled, and the quality of the tin ore to be saved.
*For tin I have not much faith in bucket dredging where there is
much overburden to deal with, but where the alluvions are of river or
creek formation and fairly clean, they are efficient in dealing with stream
tin. One has to consider the specific gravity being so much less than
gold, the material cannot be treated so fast as with gold. It is all very
well to say we can strip and elevate the overburden, then deal with the
pay dirt. That is so, but it cannot be done profitably, owing to the
delicacy with which tin must be treated. To work tin country efficiently
in the form of streaming, the gravitation system or the centrifugal pump
system is the most profitable and satisfactory. When working tin, a
long run is necessary. It is always advisable for dredge men to be
careful when working in albite granite alluvials, as tin in respectable
quantities is sometimes evident, and at times sufficient is saved to pay
working expenses of an ordinary dredge — sometimes an oxide, sometimes
a sulphuret. It will be readily understood how difficult it is to save tin
and gold when the specific gravity of tin is at 4 and 5 and oxide at
6 and 7, while gold stands at from 12 to 20, gold being seven times as
heavy as gravel, while tin is so much lighter in proportion. The per-
forated drop riffle will be found the most efficient in existence for tin,
owing to being able to set it to a dead level or fall, as required to deal
with any specific gravity. In hydraulic sluicing I have been able to
save tin and fine gold together. All alluvial men are not conversant
with tin when they get it in concentrates. Using the blow-pipe with
carbonate of soda, a globule of tin is obtained. When tin is in very
minute quantities, add a little borax, and by this means even J per
cent, may be detected.
(4) Bucket Dredge with a Sluice Box. — This dredge, although
capable of treating the same quantity of stuff as the screen bucket
dredge, is somewhat limited in operation, because it cannot work at
more than 4 feet above the water and not more than 25 feet below the
water level. It also requires, if it is to be worked at its best, a
swift current in the river to carry away the debris — the disposal of the
tailings being always the great trouble with this type of dredge. One
great advantage that this type of dredge possesses is its simplicity,
having a smaller amount of machinery to operate. On the other hand.
* H. L. Lewis " Gold and Tin Dredging Practice," 1905.
PRFDGING FOR TIN. 229
where flat stones occur in the wash it renders the working more ex-
pensive, because it causes considerable loss of ore, and necessitates
cleaning up more frequently. The most suitable wash for this dredge
is one composed of coarse gravel and small round pebbles, but under
no conditions does the author recommend this class of dredge being
installed without the previous advice of a skilled expert.
The author does not know of any of this type of dredge being em-
ployed in dredging for tin ore.
(5) Bucket Dredge with Screen and Elevator. — The dredge mostly
in use at the present day is of the endless chain screw and elevator
type. An endless chain of buckets is carried on rollers resting on a
steel ladder. 'J'he upper end of this ladder is swung on a pivot shaft
attached to a frame at a convenient height above the deck of the
dredge. The lower end of the ladder is suspended to the gantry frame
by cables, which pass over sheaves to a drum on a winch, so that the
ladder may be raised or lowered to feed the buckets. The buckets
pass over tumblers at thfe upper and lower ends of the ladder. The
power to drive the bucket line is applied at the upper tumbler through
gears. The material, as excavated by the bucket, is dumped into a
shoot, and from this shoot is fed to revolving or shaking screens. The
proper arrangement of this screening and sizing apparatus has a very
considerable influence on the successful saving of the tin ore. When
-dredging clayey matter " retards " should be riveted into the revolving
screens so as to break it up, a jet of water should constantly play inside
of the screen, which allows all rocks of from 12 in. to 24 in. in diameter
to pass out.
The best working size for the apertures in the screen is between
1 in. to 6 in. in diameter, after passing through the screen the pulp is
elevated by a large centrifugal pump, this has the effect of disintegrating
the material and is allowed to pass over a grizzley before going into the
sluice below. The distance between the bars is determined by the
nature of the material treated, but the grizzley should take out all large
heavy material which will interfere with subsequent saving operations.
This sluice is about 3 ft. wide and 2 ft, deep, it may be found
necessary to widen this sluice box to allow a larger settling area, ripples
should be placed at intervals to make an undercurrent which allows the
flne material to settle.
The same operation is repeated if found necessary again, the contents
of the sluice is passed over a grizzley, the finer material falling into a
shallow box, about 1 ft. deep from 5 to 6 times the width of the sluice,
this box gradually tapers towards the outlet. This part of the sluice
should be made 15 ft. long and from 24 in. to 18 in. wide.
This dredge, so far as its powers of working go, will treat almost
any wash, its principal features being that, as compared with the
limited range of the sluice-box machine, it can deal with wash at a
depth of 50 feet below and 50 feet above the water level, and deliver
the tailings to a height of 70 feet above the water, making a range of
100 feet in all. On the other hand, this class of dredge has more
machinery to keep up, the tables can be cleaned up continuously
230 TIN DEPOSITS OF THE WORLD.
without stopping the dredge. The principal merit in this machine is
the splendid manner in which it delivers the tailings. The question of
how to deal with the tailings was, up to a few years ago, one of the
most difl&cult problems in connection with all dredging propositions for
metals.* It remained for Mr. W. H. Cutten, of New Zealand, to
solve the problem. Up to 1894 the dredges in New Zealand (which
might be described as the birth-place of dredge mining) were only
working the river beds and low beaches, but could not work the higher
banks, on account of the difl&culty in stacking the tailings clear of the
stern. In June 1894 Mr. Cutten designed and constructed a machine
now called a " tailings elevator," which consisted of a ladder fixed to
the dredge, and projecting over the stern at an angle of about 33° to
the water level.t On this ladder there is a continuous chain of buckets,
or rather trays, working over tumblers at the top and bottom of the
ladder. The rough portions of the tailin2:s, after being washed and
separated from the fine by a revolving screen, were delivered into the
elevator, carried up, and stacked to any desired height or distance from the
stern of the dredge according to the length of the elevator. This was
the first attempt to deal with the difficulty.
The following is the latest form of Tin Dredging plant at present in
operation : —
The dredging plant at the Y Water Holes, Emmaville, N.S. Wales,
will be the largest yet erected in the Commonwealth. It will include
two pairs of compound special dredge type of engines of heavy con-
struction, designed for a working pressure of 160 lbs. per sq. in. The
bailers, three of which will be installed, will be 22 ft. long by 7 ft. 6 in.
diameter, and weighing 16J tons each. They are designed for a work-
ing pressure of 155 lbs. per sq. in. The stacks will be 60 ft. high from
footplate. The gravel pump will be of the Kershaw pattern centrifugal
pump, 14 in. intake, and will embody all the latest improvements. The
nozzle pumps, of which two will be installed, will be of 16 in. right and
left hand, of special construction, arranged to operate in series or com-
pounds, and capable of giving a nozzle pressure of about 75 lbs. per
sq. in. The whole of the machinery will be erected upon a pontoon of
* It is interesting to note the way in which the tailings from a dreige will
stack up under different conditions. A dredge with a single sluice-box, into which
the whole of the washdirt is discharged, will require about 20 per cent, more room
to Stack the tailings than they formerly occupied ; but one fitted with a revolving
screen and elevator will require fully 33 per cent, more room, due to the fact that
the fine dirt is separated from the coarse, and only gets partially mixed when
discharged at the stern by elevator. In this case the fine dirt, and all that
passes through the perforations in the revolving screen, is delivered close under the
stern of the dredge, and settled on the bottom, while the coarse dirt and stones
are carried up the elevator and stacked on top of the fine stuff, which gets no
chance of being mixed with the stones. The interstices between are not filled,
consequently much more room is required.
f The principle of the tailings elevator is evidently not quite understood by
some dredge-makers, as the author has seen some designs in which the angle of
elevation, instead of being 33°, is only 18°, which would tend to cause immense
leverage and consequent loss of power.
DREDGING FOR TIN. 231
the following dimensions : 65 ft. by 45 ft., with a depth of 5 ft. The
plant will be capable of treating from 100 to 150 cub. yds. of solid
material per hour to a depth of 60 ft.
The question of size and capacity of the dredge is one on which
opinion differs, but at present all efforts are bent towards increasing the
capacity of the dredge. The dredge of a monthly capacity of 40,000
to 45,000 yards is more easily kept in repair, for all parts are compara-
tively light. Still, the labour cost, which is one-third of the actual
expense of working a dredge, is the same in a dredge of 40,000 yards
capacity as it is in a dredge of 70,000 yards capacity. The increase in
power is in less proportion than the increase in the number of yards
handled, and therefore the larger dredge is unquestionably the greater
net producer. However, there is an economical limit to the capacity of
a dredge. At the present time this limit may be said to have been
reached in the case of dredges handling 70,000 to 80,000 cubic yards
per month. Still the tendency is to larger, and it is not at all impossible
that within a short time dredges of 100,000 cubic yards' capacity will
]ye the most economical.
There are four distinct functions which a dredge must perform : —
(1) Excavate large definite quantities of gravel.
(2) Sluice all the gravel the buckets or pump can raise.
(3) Save the tin.
(4) Dispose of the tailings.
The dredging part of the machine was developed first. The size
and strength of all the machinery had to be increased to withstand the
changing and immense stresses put upon it in dredging gravel. Actual
working experience has been the key to the problem which had to be
met. What this experience has taught may be illustrated by the state-
ment that the weight of the buckets alone has been increased from
500 lbs. to 1 ,200 lbs. each. Machinery on the dredge, as a whole, has
been increased from 150,000 lbs. to nearly 500,000 lbs. in the larger
machines, whilst the capacity of the dredges has been increased from
20,000 to 75,000 cubic yards per month.
It takes more horse-power to dredge tight gravel than it does to dig
loose gravel, and dredging large quantities of gravel necessitates an
equivalent amount of power. The question of horse-power behind the
bucket line or suction-pump is determined by the class of deposit to be
treated. In bucket dredging, as a fundamental proposition, the machinery
must be designed to withstand the maximum pull which can be exerted by
the driving machinery. If a 100 horse-power motor is driving the
buckets the strains must be figured, not to withstand the normal pull of
this motor, but the greatly increased pull as it slows down to the
standing point. To this figure add the strain resulting from the surging
of the dredge when digging tight gravel.
Variable speed motors have been generally introduced to give better
control of the machinery, and to regulate the speed of the bucket
chain.
232 TIN DEPOSITS OP THE WORLD.
The rated horse-power of the 45,000 yard dredge is up to 60 ; that
of the 75,000 yard machine is 120. The actual horse-power used is
about 50 for the small dredge and 100 for the larger one.
The " wear and tear " on dredging machinery is great, but the
wearing parts are lined largely with manganese steel, and these wearing
parts have been made readily and easily replaceable.
The dredging power of the machine was developed more rapidly
than the screening and tin -ore saving part. The dredges were digging
more gravel than they could wash and screen. However, this defect can
be overcome by increasing the screeoing, and adding more water and
greater tin-ore saving area. It is impossible to save tin in a narrow
sluice, and it is also necessary to have an adequate arrangement of
'sizing and screening apparatus. The most difficult material to sluice
being fine heavy alluvial, where this is met with the sluicing is much
facilitated by allowing a number of well-rounded stones, 4 in. to 5 in.
in diameter, to go into sluice, the result being that the fine material
does not pack so readily and allows a free action of the water. It is
a common fallacy to suppose that any dredge will answer. To be
successful the dredge must be designed to suit the conditions under
which it is proposed to operate, the amount of material to be handled,
and the character of that material.
The successful recovery of the tin ore has been a difficult problem,
and improvements in the present methods are still possible. A long
tail race is absolutely necessary for the successful recovery of tin ore.
A dredge must be kept running as near twenty-four hours a day as
possible, for when a dredge stops the producing part of the plant stops,
while the expenses continue. Good judgment in the management of a
dredge will minimise the time lost. Duplicates of the essential parts of
the dredge should be kept on hand. All wearing parts should be pro-
vided for beforehand, so that when a break occurs it can be mended
with the least possible delay. Care in this respect is more necessary
in the dredge than in the mill, for in the mill you can hang up one
battery for repairs or renewals while the others are working, but with
the dredge the most trivial accident will stop the whole plant until
repaired.
( 233 )
CHAPTER XIX,
METHODS OF TIN ASSAYING.
There is no method to compare in rapidity, cheapness, and compara-
tive accuracy with the tests made by the vanning shovel or prospecting
dish.
The former is generally used for testing the values of crushed ore
in dressing sheds, and the latter for washing oflP prospects from alluvial
drift.
Mr. Richard Pearee, in the Engineering and Mining Journal of
New York, published the following account of some investigations made
for the purpose of establishing the amount of inaccuracy that occurs in
vanning.
Mr. Pearee did all the vanning — that is, mechanical assaying of tin
ores — at Dolcoath when a young man of 20 years, so that his investiga-
tions into the methods still in vogue there, after he himself has added
more than 40 years of metallurgical work to his youthful experience,
represent results of peculiar interest to professional men.
From the above it will be gathered that Mr. Pearee is entitled to
speak with some authority. Having pointed out the difficulties en-
countered in investigations of this description, he says : " It occurred to
me, after much thought on the subject, that some reliable data as to the
extent of these tin losses might, perhaps, be obtained by preparing
(synthetically) a mixture of known ingredients, resembling in composition
and general character such crude ores as are treated in Cornwall, and
then experimenting upon it. For this purpose a gangue was selected,
consisting mainly of quartz, chlorite, small quantities of pyrite and
arseno-pyrite, and containing, of course, no tin. A sample of cassiterite
was selected from a Bolivian specimen, uniform in character and con-
taining 70*38 of metallic tin as determined by careful assay by the
cyanide of potassium method. The mixture was carefully prepared,
consisting of 150 parts, by weight, of the gangue, with 5 parts of the
rich Bolivian tin ore, by pounding in a steel mortar until the whole of
the material passed through a 30-mesh screen. Great care was taken
to prevent mechanical loss in the crushing and preparation of the mix-
ture, and the actual loss of material sustained did not exceed 0*4 per
cent. After passing through the 30-mesh screen this material was still
further ground in a mortar to a pulp sufficiently fine for the ordinary
determination of oxide of tin by vanning. The mixture prepared as
234
TIN DEPOSITS OF THE WORLD.
above should contain 3*225 per cent, tin oxide of 70'38 per cent, metallic
tin, or a total percentage of metallic tin in the crude material equal to
2*269 per cent.
" The entire sample was carefully mixed and divided into three
portions. One portion was sent to the assayer at Dolcoath, with a
request that he should determine in the usual way the percentage of tin
oxide (black tin) it contained, and return the concentrates for inspection.
The second portion was assayed, by vanning in the same way, by
myself ; and as the results appeared to disagree, the third sample was
sent to Mr. Reynolds, the instructor in vanning at the Camborne School
of Mines, for determination by vanning. The concentrated produce (tin
oxide) obtained from vanning by the two experts was returned for the
purposes of comparison. The results are shown in the following^
table : —
Dolcoath -
R. Pearce -
Reynolds -
Mean
Actual contents
" The concentrated product in each case was assayed for tin by Mr.
E. V. Pearce, of Williams, Harvey & Co., tin smelters, at Hayle, Cornwall,
after digesting for some time in HCl. for the purpose of dissolving out
any iron oxide present. The percentages of tin contained in the three
vanned products is shown in the second column.
"The Dolcoath result exhibits a low degree of concentration, which
is proved by the determination of the iron in the hydrochloric acid solution
resulting from the preliminary chemical treatment of the concentrate**
samples ; this solution gave 10*2 per cent. f'ejOg, as compared with
6' 4:6 per cent, and 2*5 per cent, found in the other samples by Pearce
and Reynolds respectively. It will be seen from the above results that
in the assay, by vanning, of an ore containing 3*225 per cent, of tin
oxide, a loss is sustained by the actual method in vogue of 21*55 per
cent., and we may reasonably infer that an ore having a lower assay
value, such as is produced in Cornwall at this time, would suffer a
correspondingly increased percentage loss in vanning. It is more than
probable that the mixture offered more favourable conditions for con-
centration, from the fact that the tin oxide was entirely free and
contained no particles of gangue attached to it, such as would decrease
the specific gravity considerably, thereby inducing an increased loss.
We may reasonably infer, therefore, that the results obtained from
vanning the mixture indicate a larger percentage of saving than can
. METHODS OF TIN ASSAYING. 235
possibly be obtained by a similar treatment of the ore in its natural
state as it comes from the mine."
The latest, best, and most accurate methods of the assay of tin ore
are published in a work called The Assay of Tin and Antimony^ by
L. Parry,* who gives the following account :—
" Tin Ore.
"The dry assay of tin ore is only to be recommended for works
purposes, mines, or for prospectors. It is not accurate enough for
buying and selling on equitable terms, having regard to the amount of
money hanging on a single assay and the increasing keenness of
competition.
" The Cyanide Assay is of the most general applicability, but (a)
where the ore is pure and contains much Fe^Oj it should be digested
with strong HCl, provided the tin is present as cassiteritc. {h) If
much pyrites is present it should be evaporated to dryness with HNOj
before extraction with HCl. These operations may be conveniently
performed in a 6-in. evaporating basin with a clock glass cover. Oxide
of lead, if occurring in tin ore, is very difficult to extract completely,
even with strong hot HCl, whilst HNOj often removes only half of it.
Take 20 grms. dried ore, 20 c.c. of strong HNOs, ^^^ about the same
amount of water, and evaporate cautiously to complete dryness. Add
100 c.c. strong HCl and digest for half-an-hour just below the boiling
point. Dilute with an equal bulk of water, filter, and wash by decanta-
tion until the washings are free from HCl. Ignite the filter paper
and add the ash to the cleaned residue of ore in the dish. The HCl
extract will usually contain most of the iron, arsenic, antimony, etc.,
and will in general be free from tin, but should always be tested or
assayed for tin (see wet assay). It is never safe to assume that the
cleaned residue is free from metallic oxides other than SnOj, though the
assumption is frequently made. Dry the cleaned ore and mix it with
an equal weight of cyanide (98 per cent. Au — not commercial cyanide).
Take a small dry crucible and charge in 10 grms. cyanide, then the
above mixture, and finally 10 grms. cyanide as a cover. Place in a fire
at a low red heat and fuse gradually, increasing the heat to bright red-
ness at the finish of the fusion, which should not take more than ten
minutes. Allow the assay to become quite cold in the crucible, and
when cold break out the button, and either re-melt it by dropping it into
a crucible containing melted borax, or under palm oil in a ladle, or cut
it in two and boil out the adhering cyanide with water. The button
should in every case be assayed by a ivet method for <«w, otherwise the
result is a mere guess and may be very misleading, no matter how much
the ore has been cleaned or however pure the ore is supposed to be, or
however clean the metal appears to the eye. The use of the term " fme
tin " has been already referred to in the introduction, and it is only
necessary to add here that Sn is a definite entity, while " fine tin " is an
* L. Parry, " The Assay of Tin and Antimony." (London : " The Mining
Journal.")
236 TIN DEPOSITS OF THE WORLD.
expression which awaits definition. Further, it is quite as bad to assay
such a button by oxidation with HNOj and weighing the oxide residue
as SnOa — that would be merely making the same unjustifiable assump-
tions (in another form) as to absence of certain impurities, which are
involved by weighing the prill as tin. The button must be assayed
positively for tin by a method which shall ensure the elimination of the
interference of every possible impurity, and that, in practice, means
assaying the button for tin by a volumetric method. Of course, if this
procedure is systematically followed — (and any other is illogical as an
assay, and so uncertain as a valuation basis as to be inexcusable on
account of the high price of tin), the results will always favour the
buyer. The remedy is not to attempt to counteract this " low " tendency,
which is inherent in any dry assay, by balancing an unknown " high "
tendency (impurities) against it (the net result of which is, in practice,
to favour the seller), but to use a wet assay throughout.
" Of other dry methods of assaying tin ore, the Cornish tin assay is
no doubt useful on mines as a comparative test, where the quality of the
ore remains fairly uniform, whilst the vanning test is also most useful
to prospectors and on mines,
" The German assay of tin ore by mixing with oxide of copper and
fusion for white metal does not appear to possess any advantages over
the cyanide assay as regards accuracy, and is an exceedingly complicated
method.
" The method of fusing tin ore with Na2C08 and borax in a luted
carbon-lined crucible, in the muffle, is said to give very perfect reduction
of the tin.
" Hallet's method — fusion with KHFj, solution in H2SO4, and pre-
cipitation of the tin as metastannic acid on dilution and boiling, seems
to be a good assay, but is in reality a wet method.
" The Wet Assay of Tin.
*' Gravimetric Assay hy Weighing as SnO^,
" Bi, Pb, As, Sb, Fe, W, Si, should be absent.
"The tin from 1 grm. of material, separated either as metal or
sulphide, is treated with 20 c.c. of dilute HNOj (1 : 1) in an evapora-
ting dish, and evaporated almost to dryness. It is diluted with 50 c.c
hot water and boiled, then filtered, the residue well washed with hot
water, dried, and ignited in the muffle in a small porcelain dish. When
cold, weigh the SnOg. It contains 78*7 per cent. Sn.
" The tin in bronze coins and tin copper alloys free from Sb, Pb,
As, may be estimated this way, but its application to solder, metal from
crucible assays of tin ore, and the sulphide precipitate from tin slags is
inaccurate.
" If solder is treated in the above manner, the residue consists of
SnOa and SbO^j and some PbO. Multiply the weight of residue from
1 grm. of solder by 78*7, and the result, less 1 per cent, deduction for
METHODS OF TIN ASSAYING. 237
lead, may be taken as the sum of the percentages of tin and antimony ill
the solder.
" Gravimetric Assay by Ehctrolysis,
" This assay is fully described in Classen's Chemicil Analysis by
Electrolysis.
" Volumetric estimation with Ferric Chloride,
" When ferric chloride is added to a strong HCl solution of stannous
chloride it is immediately reduced to ferrous chloride, and stannic chloride
is formed at the same time. One drop in excess of the ferric chloride
gives a decided yellow colour to tlie previously colourless solution, pro-
vided the solution is hot and strongly acid. The nearer the boiling
point and the greater the concentration of HCl in the solution, the more
rapid is the completion of the reaction. A solution of FeClg in dilute
HCl, of which 100 c.c. = 2 grms. Sn, is employed. In the assay the
addition of FeClj from the burette cools the solution somewhat, so that
the fiuish is rather slower than the commencement of the reaction, both
owing to dilution and consequent lowering of the temperature, and to
the presence, in increasing concentration, of ferrous chloride in the
solution, but in any case the titration should never take more than a
minute if worked as directed. FeClg gives a far stronger colouration in
a hot, strongly acid solution than in a cold,. faintly acid solution. The
titrations cannot be done by gas light or electric light, and should
always be effected in the day time. In an emergency they may be done
by magnesium light.
*'The equation representing the chemical change is 2 FeCl, +
SnClg = 2 FeCl2 + SnCl^ The presence of chlorides of lead, zinc,
aluminium, iron (ous), cobalt, nickel, antimony, (ous), copper (ous),
cadmium, does not affect the quantity of FeClj required ; the presence
of FeCl2 in quantity somewhat retards the finish and lessens the
delicacy of the colour indication ; CU2CI2 reduces FeClg with forma-
tion of CuClj, but SnCl2 reduces CUCI2, and the net result of this is
that not a trace of CUCI2 is formed until all the SnCl2 is converted ,
into SnCU — the next drop of FeClj forms a trace of CUCI2 which gives
a similar colour indication to that of FeCl^ itself ; CoClj and NiClj
give highly coloured solutions which render the recognition of the end
point difficult — one way of remedying this is to dilute the solution
somewhat with boiling water, which removes the blue colour, but of
course renders the reaction slower, and lessens the colour intensity of
the drop or two excess of FeCls ; SbClg is not converted into SbClg by
FeClg, and under the conditions of the assay neither SbClg nor SbCls
ever occur in the solution. Cug CI2 CoClj, NiC]2 are rarely present,
also CdCl2 and AlgCJe ; FeCl2 is often present to begin with, and ZnCl|
and PbCl2 are generally present in greater or less amounts. BiClj and
HgC]2 are reduced to metal by SnCl2» but Bi and Hg would be separ-
ated with iron. Precipitated Sb, Cu, As, are attacked by hot acid
ferric chloride and blue oxide of tungsten is affected by it, but the assay
method excludes the presence of these substances during titration.
238 TIN DEPOSITS OF THE WOULD.
Acid solutions of SnClj very readily oxidise by exposure to air ; the
method of dissolving the tin from the state of metal by boiling with
HCl in an atmosphere free from oxygen excludes the formation of
SnCl4 if the operation is carried out as subsequently directed, and if
the solutions are titrated as soon as ready and at the boiling point, the
oxidation tendencies are completely eliminated. Briefly the best con-
ditions are ( 1 ) Solution from the state of metal as rapidly as possible in
a non-oxidising atmosphere, the solution being brought to the boiling
point before solution is complete. (2) Use of strongest and purest
HCl. (3) Bulk 150—250 c.c. (4) Titration rapid and at the B. Pt.
(5) Strength of FeClj 103 c.c. = 2 grms. (6) Absence of precipitated
Sb, As, Cu in the solution.
" From the dihite peroxidised HCl solution of Sn, Sb, Hg, Bi, As,
Cu, Pb, Cd, Zn, Co, Ni, Fe, P, the Sn, Sb, As, Cu, Hg, Bi, and some
Pb and Cd are separated as sulpljide by HjS if it is desired to sepante
from Co, Ni, Fe, P. The sulphide precipitate is re-dissolved in HCl and
KCIO , and the solution reduced by heating with iron wire. The As
Sb, Cu,Hg, Bi, are precipitated in the metallic forpi, and the solution
(which must be strongly acid to avoid precipitation of SnOCl2) is
filtered and neutralised with thin strips of zinc. The action finished,
the mother liquor, after testing for tin with HjS water, is poured off
as completely as possible, and the residue of spongy metallic tin and
lead and undissolved zinc is dissolved in the same flask in about 200 c.c.
of pure HCl, the flask being provided with a rubber cork and leading
tube, and the liquid is brought to a boil as rapidly as possible ; a piece
of pure zinc about the size of a pea is added to assist in preserving a
non-oxidising atmosphere of hydrogen and hydrochloric acid in the
flask until the liquid clears and boils. As soon as everything is in
solution and the liquid is boiling, the flask is removed from sandbath or
plate and titrated immediately with ferric chloride. The ferric chloride
should be free from ferrous chloride, nitric acid, chlorine and arsenic,
and the sokition should contain 300 — 500 c.c. HCl in two litres. It is
best made up from a concentrated stock solution in HCl, made by
dissolving piano wire as directed subsequently. If the assays turn dark
greenish after titration, the FeClj solution is contaminated with HNOa.
The FeClj may be made up also by dissolving 180 grms. of the yellow
commercial lump salt, which is Fe^ Cle 12 HgO, in about 200 c.c. HCl
and evaporating it to dryness. The residue is dissolved in 300 c.c.
HCl, and diluted to two litres. The solution is standardized against
one grm. of the purest tin obtainable, filel with a fine file. This is
weighed into an 8 oz. flask, and the flask is about three parts filled
with pure HCl, rubber cork and leading tube inserted, and boiled (but
not too rapidly) until solution is complete ; then titrated at once.
" Pure tin is more readily obtained from smelters of tin ore than from
dealers in chemicals. The writer once ordered some " pure tin for
standardizing purposes " from a firm of wholesale chemists, and received
metal holding three per cent. Sb.
" It is rarely necessary to complicate the assay by separating the tin
as sulphide. Having once got everything in solution, reduce with iron
METHODS OF TIN ASSAYING. 239
wire, filter, and precipitate on zinc. This method has been repeatedly
checked on made up metals of known composition containing varying
amounts of Sn, Pb, Cu, Sb, and the results are in every case so close as
to leave no doubt whatever that the method is extremely accurate;
indeed it is much more accurate than the electrolytic assay, on account
of the complicated separations which the latter involves, and is incom-
parably quicker.
" The favourite objection to the feme chloride assay is the oxidation
tendency of solutions of SnClj. The method, if properly worked, over-
comes this completely. It has also been objected that five or six drops
of ferric chloride solution are necessary to give a perceptible colour
indication. This is quite incorrect ; one drop in excess of FeClj is
ample if the operator possesses normal colour vision. It is also stated
that Sb dissolves in HCl ; this is not the case. It is true that finely
divided Sb in contact with air and HCl slowly dissolves, but even then
FeClj does not oxidise SbCls ; and further, under the conditions
of the assay the absence of Sb is ensured by the iron wire separa-
tion. In direct ferric chloride assays on solutions from metal filings,
the assays, so far from being too high through Sb dissolving, are
too low because of Sn retained with the black powder, and it should
also be remembered that metallic tin precipitates antimony from
solution.
" Volumetric Estimation with Iodine in Acid Solution.
" The dilute acid solution of metallic chlorides, which should not be
more than about 50 c.c. in bulk, and should be contained in a 4 inch
beaker, is reduced by heating with a clean piece of iron rod resting in
the solution against the side of the beaker, which is covered by a watch
glass. The whole is heated to 80° or 90° C. (not to boiling) over a
Bunsen flame ; five or six assays may be conveniently heated in a
small frying-pan sandbath. The assays are heated for 20 — 30 minutes
after they have lost their original red, yellow, or greenish colour. The
Sb, As, Cu are precipitated, and the SnCl4 is assumed to be reduced to
SnCIg ; in practice this assumption is found to be justified, though it is
really one of the weak points of the assay. The assays are cooled in a
basin of cold water, and when cold the watch glass and rod are rapidly
washed with a little cold boiled water, starch paste added, and the
solution titrated rapidly with iodine. It is not necessary to remove the
black precipitate of Sb, As, Cu, as the finishing point in the case oi
Sn Clj and iodine is so sharp ; but the finely divided metallic precipitate
sometimes seems to slowly remove the blue colour. The iodine solution
is made up by dissolving 21*32 grms. iodine and 45 grms. pure KI in
about an inch of water in a small beaker and diluting to one litre.
100 c.c. = 1 grm. Sn. Not more than '5 grm. Sn should be present in
the assay. It has been proposed to increase the accuracy of this assay
by titrating in an atmosphere of CO2."
240 tin deposits of the wokld.
Assay of Tin Ore.
Tin ores are often exceedingly complex ; they may contain in
addition to stannic oxide, ferric oxide, and silica, some or all of the
following substances — bismuth, copper pyrites, iron pyrites, mispickel,
wolfram, titanic acid, lead oxide, antimony oxide. Antimony and
arsenic are common impurities, especially in South American ores.
Contrary to a statement in " Crookes' Select Methods," the writer's
experience is that antimony is almost invariably associated in small
quantities with tin ore. It should be apparent that complete solution of
the ore is absolutely essential in every case, in order to systematically
ensure the complete extraction of the tin and its quantitative determina-
tion. Any method which does not involve complete solution of the ore
is quite unreliable as a method^ although it may often yield correct
results. Further, the final determination of the tin should always be
effected volumetrically ; if a gravimetric estimation is adopted the assay
develops into an academic research, owing to the number and compli-
cated nature of the separations necessary to ensure that no possible
impurity may score as tin ; while if such thorough separation is
neglected, the results obtained are quite unreliable.
The following methods have been proposed and used for the wet
assay of tin ore : —
1. Fusion with alkalies or alkalies and sulphur.
2. Continued agitation with zinc and HCl.
3. Reduction of the cleaned stannic oxide in hydrogen and calcula-
tion of the tin from the loss in weight, which is assumed to
represent only the oxygen of the stannic oxide.
4. Cleaning with HCl, and reduction with cyanide in a porcelain
crucible.
o. Fusion with potassium hydrogen fluoride, solution in sulphuric
acid and precipitation as metastannic acid by dilution and
boiling.
6. Reduction in coal gas or hydrogen, and extraction with HCl and
HNOj, combined with fusion of the siliceous residue with
Naj COa and borax in a platinum crucible and solution of the
melt in HCl.
The first method is now hardly ever used, being tedious and
uncertain. The second method, agitation with zinc and HCl, is very
slow ; it may occasionally give all the tin, but there can be no certainty
whatever about such a method, and the same remark applies to the
third method, calculation of the tin from the weight of oxygen lost by
reducing the stannic oxide in hydrogen after presumably purifying it
from other metallic oxides by cleaning the ore with acids ; rapidity is
claimed for this method, but the assumptions as to complete reduction
of the tin and absence of other metallic oxides reducible by hydrogen
are vital objections, and render the method unsound from both a scien-
tific and commercial standpoint. Method four, reduction of cleaned ore
with cyanide, is in reality a dry assay, notwithstanding the use of the
porcelain crucible, and when the metal obtained is assayed for tin, must
METHODS OF TIN ASSAYING. 241
necessarily give results which are lower than the tin contents. It is not
denied that in many cases the results will only be very slightly under
the actual percentage, but one can never be certain of this ; often,
indeed, results obtained in this way are two or three per cent, too low.
If the button of metai is not assayed for tin, the results obtained may be
either a little too low, correct, or up to as much as four or five per cent,
too high. The method is not sufficiently certain for the commercial
valuation of tin ores. Method five (Hallet's method) is logically admis-
sible, provided that the precipitated metastannic acid is not merely
ignited and weighed as stannic oxide, but is redissolved and the tin
carefully separated. This, however, complicates the method somewhat^
Method six is the most practical method of assaying tin ore, which,
ensures at the same time accuracy and reliability as a method ^ and it
alone will be considered here.
Description of Method.
Tin ores may be either pyritic or non-pyritic. Pyrifcic ores must be,
and non-pyritic ones may be, treated with HNO, before reduction, as
sulphide of tin is volatile at a red heat. Five grms. ore, ground as finely
as possible in an agate mortar, is treated in an evaporating basin with
clock glass cover with 20 c.c. dilute HNOa, and carefully evaporated to
complete dryness. The residue is digested with dilute HNOj and
filtered. The washed residue is dried, ignited in the dish, transferred
to a porcelain boat and heated to a low red heat for 3 to 4 hours in a slow
current of hydrogen or coal gas. Coal gas is much more convenient to
use, and quite as effective as hydrogen. The boat is 2\ inches by
\ inch, and two at a time are placed in a porcelain tube 12 inches long
and f inch bore, which is then placed in the reduction furnace. A
very convenient form of gas reduction furnace with clay body, brass gas
jets, and asbestos rings to fit over the ends of the tube against the clay
covers, is made in 6-inch lengths by Messrs. Fletcher, Russell & Co. of
Warrington. The ends of the tube should project about 3 inches from
each end of the furnace, and should be closed with rubber corks fitted
with glass tubes as shown ; the escaping gas (about 2 bubbles per
second) is passed through dilute HCl.
C£J^ ^ 7^ T- =l=g
Fig. 36.
The water through which the gas escapes should not be thrown
away, but saved, and every now and then the tube should be washed out
with HCl and KClOj, and the two solutions tested for tin as a check,
against, for instance, loss by volatilisation through sulphur in the coal
Q
242 TIN DEPOSITS OF THE WORLD.
gas. A two-way gas branch is used ; one jet supplies gas to the tube,
the other supplies the gas for heating to the jets of the furnace. The
boats are allowed to cool in the furnace, and when cold each boat and
its contents is transferred to a 400 c.c. beaker and treated with 100 c.c.
HCl and 5 c.c. HNOj, the assay being allowed to stand in a warm place
until the action abates, when it is boiled for a few minutes, diluted with
an equal bulk of water and filtered. The residue is well washed with
hot acid water, then with hot water, is dried, ignited and fused with
four or five parts of a mixture of fusion mixture (free from chlorine)
and borax in a platinum crucible, and the melt dissolved in HCl and
precipitated with zinc as usual. The residue rarely holds more than
a half per cent, of the total in the ore.
" The main solution is made up to 500 c.c. and the equivalent of
1 grm. is pipetted into an 8-ounce flask, reduced with iron wire and
filtered ; the filtrate is precipitated with strips of sheet zinc as usual,
and the metallic sponge dissolved in HCl and titrated with ferric
chloride."
Any copper in the tin ore is found in the HNOj solution, though
traces may remain with the SnOj. In the iron wire stage, the arsenic
which escaped extraction with HNOj and volatilisation in the reduction
tube is partly evolved as AsHj, and partly precipitated with antimony
in the metallic form. It comes down as a brown flocculent deposit
which contains three or four per cent, of its weight of tin. As there is
generally only a few per cent, at most of As in a tin ore, the loss of
tin from this cause is quite negligible, but as a check one should save
the iron wire and precipitates and filter papers and examine them from
time to time for tin. It will be found, as in the case of the deposit in
the tube and the dilute HCl through which the escaping gas bubbles,
that only the merest traces of tin are lost in these operations. Further
the HCl solution of the reduced metal may be done in a conical flask
with rubber cork and leading metal tube dipping under water, to assure
oneself that there is no appreciable loss by volatilisation of SnCl4.
If the ore contains wolfram, the tungsten is mostly found as WOj
in the residue from HCl and HNOs extraction of the reduced metal,
from which it may be removed before fusion, with AmOH. Any
tungsten which gets into the main solution comes down as blue oxide
with the iron wire precipitate, and any which is fused with KNaCOg
and borax should be removed by reducing the HCl extract of the melt
with iron wire, before precipitating with zinc. In general, all the
antimony and some of the lead in the ore will be found in the main
HCl solution, whilst some of the lead will be obtained in the HNOs
extract.
Note. — After the HNOs evaporation the residue may be boiled with
HCl (40 or 50 c.c.) diluted and filtered, though in this case the extract
must be tried for tin as a matter of precaution. It will in general hold
all the copper and most of the arsenic, antimony, lead, and iron, though
one can never be sure that the residue is free from the oxides of these
metals. Occasionally this HCl extract will hold a little tin. The
residue is reduced in the usual manner.
METHODS OF TIN ASSAYING. 243
One of the most difficult assays in tin is to accurately determine the
amount lost in the sluices and tailings. On that account the method
given below is of great practical value ; it was published in a paper by
George L. MacKenzie before the Institution of Mining and Metallurgy,
November, 1903.
Method.
Clean the ore with aqua regia. Reduce the stannic oxide to tin
by ignition in an atmosphere of coal gas (used as hydrogen). Dissolve
out the tin with hydrochloric acid and free chlorine. Precipitate as
stannic sulphide by passing hydrogen sulphide. Convert the stannic
sulphide to oxide by ignition in a small weighed Berlin crucible and
weigh as stannic oxide.
Take from 1 to 5 grm. ore according to richness so as to get a
weighable quantity of stannic oxide — 1 grm. of a 2% ore is sufficient :
if the ore is very poor two lots of 5 grm. may be combined after
reduction separately in the combustion tube.
Crushing must be very fine, the sample well mixed and not shaken
about afterwards, or the tin oxide will get concentrated in the lower
part of the sample. In quartering samples the finest dust left on the
sampling paper will probably be the richest.
1. Cleaning the Ore, — Cover assay with aqua regia in beaker or
evaporating dish : heat nearly to boiling point for about twenty minutes
— longer if wolfram is present. Dilute with hot water. Filter hot and
wash well with hot water, especially if any lead is present in the ore.
If there is tungsten or silver in the ore, digest the residue for about
ten minutes with warm dilute ammonia ; filter again and wash well
the portion on the filter with the same reagent. Dry residue and
brush most of residue off the paper. Burn the paper and add the ash .
to residue.
Note. — The solid residue from aqtia regia consists mainly of silica,
stannic oxide, small amounts of iron oxide, various insoluble silicates,
and possibly sulphur and insoluble chlorides and oxides produced by
the acids used. It is essential to remove here those which will not be
removed in subsequent stages of the assay.
If tungsten is present in the sample, probably as wolfram or
scheelite, the residue will contain tungstic acid, a yellow solid readily
soluble in ammonia. This, if not removed, will count as stannic
oxide, giving a high result. Wolfram, even when very finely
powdered, is only slowly attacked by aqua regia, and time must be
allowed for this. After treatment with ammonia, niobic oxide, a white
solid derived from columbite, may still remain, but it is unlikely to be
present in sufficient quantity to seriously affect results. If its presence
is suspected the substance weighed as stannic oxide may be tested for
it and also for tantalic oxide.
2. Reduction of the Stannic Oxide to Tin, — Heat the assay to
dull redness for about forty minutes in an atmosphere of coal gas —
SnOa + 2H2 = Sn + 2H,0.
<^2
244 TIN DEPOSITS OF THE WORLD.
Note. — A combustion tube works perfectly although it is incon-
venient to manipulate. Poor ores in 5-grm. lots may be placed direct
in the tube. Rich ores in 1-grm. lots can be placed in china boats to
avoid loss in getting them out of the tube. To place a o-grm. charge
in the tube, it is convenient to have a tin spoon of semi-circular section
with a long . wire handle. (See accompanying sketch of the
apparatus).
Commence passing gas first. When all air has been expelled from
the tube, light the jet at its outer end, then warm the tube from end to
end, place the Bunsen (a large fish-tail) under the assay and cover the
tube with a bent sheet of asbestos to retain the heat. Complete reduc-
tion of all the stannic oxide in a large charge may be assisted by
slightly turning the tube round once or twice to better expose the
lower part of assay to the gas. Carbon is reduced from the gas and
darkens the assay, but does not interfere. If any tungsten "is present
it will be partly reduced if the temperature is high, and will give a high
result. Any iron present is reduced, but is removed in filtering after
passing HjS at a latter stage. After reduction is complete extinguish
the Bunsen, but leave the gas passing until the assay is cool enough not
to re-oxidise on admission of air. Most of the charge can then be
r
, , , 'wi
C=^=j^
D
m- 1
"[-'■lift
J-^^=^'
■
< ,
,| Sulphuric
Acid.
,,„_„ ,,__f It
PIG. 37.— TIN ASSAY,
Apparatus used for 5-grm. charge.
(froH gauze supporting tube and asbestos sheet covering it are not shown.)
poured out of the tube and the remainder cleaned out by a rod with a
cork on its end if the sample is poor ; or washed out with hydrochloric
acid if rich.
3. Solution of the reduced Tin, — Transfer assay to a beaker*
Cover with strong hydrochloric acid and add about 2 c.c. of a 10%
solution of permanganate. Heat nearly to boiling for about twenty
minutes, stirring occasionally. Add a few drops of permanganate
towards the end. Dilute, filter into a beaker, washing residue well.
!NoTE. — In this step all metals present are converted to chlorides,.
e.g. :— Sn + 2HCI = Sn CI2 + H^. Then Sn Cla + CI, = Sn C^
METHODS OF TIN ASSAYING. 245
The chlorine, liberated by the permanganate, assists in the solution of
the tin and further converts it to the stannic condition.
4. Precipitation as Stannic Sulphide. — Partly neutralize the
filtrate by adding sodium bicarbonate cautiously until effervescence
becomes less brisk, but the filtrate must remain acid. Pass hydrogen
sulphide. The precipitate is stannic sulphide and should be yellow
or brownish yellow. Allow assay to stand as long as convenient — over-
night if possible — to allow precipitate to settle and clot. Filter on
small ashless paper. Wash well with solution of ammonium acetate con-
taining a little free acetic acid. The sodium salts now present should
be completely washed out.
Note. — As strong hydrochloric acid attacks stannic sulphide, it is
better to reduce the acidity as above. The solution must remain acid
to keep up metals other than tin. The precipitated sulphide is very
finely divided and apt to pass though the filter paper ; this is partly
counteracted by allowing the precipitate to settle and clot, and also by
the sodium chloride produced by the addition of the carbonate.
5. Conversion of the Stannic Sulphide to Oxide, — Dry thoroughly
the paper containing the precipitate, which will darken considerably.
If small in quantity all had better be left on the paper. Holding
the paper between a small pair of forceps, burn it as completely as
possible and drop the ash into a small weighed Berlin crucible. Add
one or two drops of nitric acid and heat gently until dry. Ignite over
blow pipe, first gently, then strongly. Cool and weigh as stannic
oxide.
Note. — The sulphide can be burned to oxide without the addi-
tion of nitric acid, but loss may occur, as the sulphide is slightly
volatile.
Test Assays.
For these prepare artificial ores of pure silica and stannic oxide.
The former, if ignited, is very hydroscopic, so must be kept in a
stoppered bottle. The latter must be tested for purity, and had better
be prepared from the purest tinfoil obtainable, by boiling in nitric acid,
filtering, and washing with hot water until filtrate gives no precipitate
(PbS) with hydrogen sulphide.
A 1% ore and a O'o% ore should be sufficient, and after a little
practice an assayer should be able to get the full tin content out of these
samples, but must be on his guard against some of the very finely divided
silica passing through the filter.
The hydrogen reduction can be checked by saving the residue and
re-igniting in the tube. This should not be omitted where close
accuracy is required, and, in ordinary practice, time can be saved by
adding the solution thus obtained in stage 3 from the residue to the
similar solution already obtained in stage 3 of the assay, and then
passing hydrogen sulphide through the combined solutions.
The tendency in most steps of the assay is to get low results, and
the manipulation requires time and patience, but the assayer who
works on artificial oies of known tin contents until he can trust
246
TIN DEPOSITS OF THE WORLD.
himself will be satisfied with the method for the purpose of mhie
assaying.
Low results arise from incomplete reduction, incomplete solution
of the reduced tin, and volatilization of the sulphide by too-hurried
ignition. Of these the first is most probable, and an assay er would be
wise to at first save the residues from stage 3, re-reduce them in the
tube and run tbem as separate assays, thus determining for himself
the probable error due to this cause in the ores of his mine. The
greater the proportion of silica present the less complete is the reduction
apt to be. In reporting results, it should be borne in mind that
"black tin" is impure stannic oxide, the actual tin content varying on
different mines.
The last series of assays run by the writer gave the following
results, 4 grm. ore being taken for each experiment : —
stannic Oxide got.
Stannic Oxide recovered from
Residuea by a Second Reduction
in Tube.
Grams. ' Percentage.
Grams.
Percentage.
0-230 0-575
0-230 0-575
0238 0-595
0-230 1 0-575
0-0020
0-0031
0-0031
0-0033
0-050
0-077
0-077
0-082
Total
Percentage.
The residues from Nos. 1 and 2 were reduced a third time in the
tube, but only a trace of tin was got.
To illustrate the interference due to wolfram, four charges of 4 grm.
each were taken from the above sample ; to each 0*01 grm. taken from
a crystal of wolfram was added, and the residue from aqua regia was
not treated with ammonia, the results being the following : —
stannic and Tungstic Oxide got.
Recovered from Residues by a Second
Reduction in Tube.
Grams.
Percentage.
Grams.
Percentage.
0-0292
0-730
1 0-0030
0-0254
0-635
j 0-0032
00262
0-655
Not re-reduced
0-0270
0-675
1 Not re-reduced
0-075
0-080
The writer has to thank Mr. J. Caspell, of Camborne Mining
School, for valuable suggestions, and Mr. J. C. Montero, Assayer at
Dolcoath Mine, for kind assistance with experiments.
METHODS OP TIN ASSAYING. 247
The foUowiug paper on the assay of tin was read by J. H, Collins
before the Institution of Mining and Metallurgy in May 1904 : — *
" For practical purposes on the mine there is no method of assay
known which is likely to supersede vanning ; for, although the weight
of * black tin ' obtained from a given sample by different operators may
vary considerably, the actual quantity of contained metal will be in
skilful hands very nearly the same.t For scientific estimations the old
Ecole des Mines method of reducing by fusion with KCy and weighing
as metallic tin is easy and accurate. +
" In the assay of ' black tin ' by the direct fusion method a previous
cleansing by boiling with acid is often recommended, the supposition
being that cassiterite is altogether insoluble under such treatment.
This, however, is by no means the case ; in fact, I long ago noticed
that some varieties of natural peroxide of tin were very freely soluble
in HCl when in a fine state of division, and that even when HNOs had
been added to the HCl, some tin was apt to go into and remain in
solution for a considerable time.
" Early in the year 1903 a very distinguished metallurgist wrote me
from the United States to the following effect : —
" ' You will probably be surprised to learn that native oxide of tin
may be dissolved completely in dilute HjSO^ in presence of zinc. I
presume it is the nascent hydrogen which does the work, but if anyone
had suggested to me the possibility of such a method being applicable
to native tin oxide, I should have used " strong language" ; but we live
to learn.'
" Remembering my previous experiences of the solubility of cassi-
terite, I believe I mentioned this remarkable statement of my metal-
lurgical friend to some members of this Institution before making any
further experiments, but lately I have made a few tests, the results of
which seem to me decidedly interesting. I began by taking half a grm,
of five different substances § in fine powder, reducing them by KCy in
* J. H. Collins, " Trans. Inst. Min. and Met.," May 1904.
f See remarks by the author in the discussion of Mr. Mackenzie's paper
(" Trans. Inst. Min. Met.," Vol. XIII., p. 94), and also experiments reported by
Mr. Richard Pearce {Eng. and Min. Journal^ p. 117, Jan. 21, 1904).
X If lead, bismuth, arsenic, antimony, tungsten or other bases of group 2 are
present, proper means must be taken for their elimination before or after the
reduction, but many samples of black tin are obviously free from these bases, and
may therefoie be thus assayed direct. If much silica is present the tin will not
readily form one globule. In such cases the whole fusion should be dissolved in
hot HCl, and the tin precipitated by H2B, when the sulphide may be calcined, or
reduced before weighing in the ordinary way.
§ No. 1 consisted of clean light -coloured crystals of cassiterite, from Great
Wheal Fortune in Breage.
No. 2, closely dressed " black-tin," of a fine brown colour, from Wheal Metal in
Breage.
No. 3, reddish-brown wood-tin, from Mexico.
No. 4, greyish-brown wood-tio, from Bolivia.
No. 5, a dark brown mixture of wood-tin and cassiterite crystals, from Wheal
Metal.
248 TIN DEPOSITS OF THE WORLD.
a porcelain crucible, dissolving the fusion in hot HCl, precipitating hj
HjS, igniting the precipitate, and weighing as SnO^.
" No. 1 was found to contain 99*2 per cent, of peroxide of tin ;
No. 2, 94*0 per cent. ; No. 3, 68*0 per cent. ; No. 4, 76*0 per cent. ;
and No. 5, 94*5 per cent.
. " Half a grm. of each sample, in very fine powder, was then placed
in a beaker with 20 c,c. of dilute HjS04 (1 t^ 5), and 2 grm. of pure
zinc, and left overnight. The solutions thus obtained were boiled,
precipitated with H,S, the precipitates collected, ignited and weighed,
giving quantities of SnOa as under : —
No. 1 gave 3 mg. = 0*6 per cent, of soluble (out of 99*2 per cent.).
. No. 2 gave 9 mg. = 1*8 per cent, (out of 94*0 per cent.).
, No. 3 gave 160 mg. =: 32*0 per cent, (out of 68*0 per cent.).
No. 4 gave 360 mg. = 72*0 per cent, (out of 76*0 per cent.).
I No. 5 gave 81 mg. = 16*2 per cent, (out of 9 4* 5 per cent.).
Similar treatment with dilute HCl gave very similar results."
New Method to Separate Antimony and Tin.
* The numerous known methods to separate tin and antimony are
delicate and complicated. The following process, invented by M. A.
Czerwek, is more simple, though as accurate, but not applicable in all
cases. Its principle is to dissolve the alloy in a mixture of nitric and
tartaric acids at precipitate, at boiling point, the tin by phosphoric acid,
all the antimony remaining in solution, Digestion is operated in a hot
place with 0*5 gramme of alloy in a solution composed of 15 cubic
centimetres of HNO3 (1*42) ; 15 of water and about 6 grs. of tartaric
acid, all heated to 50 deg. C. After a maximum of 3 hours the
solution is complete. Then all is heated briskly until ebullition
commences, and while agitating 5 to 30 drops of 45 per cent, phosphoric
acid (xd 1*3), according to amount of tin, are added. Dilution is made
with 300 cubic centimetres of boiling water, and then the mixture is
let deposit in a bain-marie. The clear liquor is then decanted on a
filter, the gelatinous precipitate being washed with hot water containing
nitrate of ammonia. The precipitate is placed in a beaker-glass, yet
humid, and the residue on the filter dissolved with Am^S hot and all
united. The precipitate having been totally dissolved in heating, it is
let cool completely, then diluted with a rather large volume of water
and Sn precipitated with H3SO4. The greenish-grey precipitate is let
deposit in a bain-marie, then the liquid is decanted and washed on the
titrated water filter. After drying, the filter is separately incinerated
in a tarred qrucible, apd the precipitate is added ; oxidisation is effected
with HNO3 (d = r42), then evaporation in a bain-marie, calcination,
and weighing in form of SnO^. The filtrate, after separation of Sn, is
* Ucho des Mines^ November 29, 1906.
METHODS OF TIN ASSAYING. 249
neutralised with NH3, mixed with AniaS, then acidified with acetic
acid. The antimony sulphide precipitated is, after deposit in the bain-
marie, filtered while hot, washed in nitrated water, and redissolved
humid with Am^S. The liquor is evaporated in a large porcelain
crucible, then oxidised with fuming HNO3, evaporated to dryness, and
HaS04 expelled by heating on asbestos. Then the crucible is heated
on a non-lighting fiame, somewhat sharply finally, and the tetroxide is
subsequently weighed. When the alloy contains other metals than Sn
and Sb, work is the same. Once the tin precipitated, the precipitate is
washed with hot water on a filter, then with 150 to 200 cubic metres
of normal nitric acid hot. Residue on the filter is dissolved by Am^S
(or Na^S in presence of copper), all being united in a beaker glass.
After solution the liquor is again filtered on the same filter to retain
traces of insoluble sulphides, washing is operated with the diluted
solution and precipitation of Sn by H,S04. ^^^ filtrate containing Sb
and the other metals is then neutralised, mixed with NaaS or Am^S,
according to cases. After deposit in the bain-marie the precipitated
sulphide is filtered and washed. Finally Sb in the filtrate is precipitated
with acetic acid.
Extraction of Tin from Dross J^ — According to a patent taken out
by H. Brandenburg and A. Weylahd,! tin is separated from dross, slag,
and Avaste in the following manner : — The powdered dross is mixed
with water, and treated with a mixture of one part of hydrochloric
acid with two parts by volume of sulphuric acid, no extraneous
heating being needed ; and the tin dissolved is separated from the
filtered solution by known means. Sodium chloride may replace
hydrochloric acid in the process ; or the sulphuric acid may be
replaced by sodium bisulphate, in which case the mixture will need to
be heated.
Treatment of Scrap Tin, — It is reported that there are seven works
in Germany operating the electrolytic process for recovering tin from
scrap. Sodium hydrate is the electrolyte generally used. There is also
one plant in Austria, and one at Manchester, England. About 30,000
tons of scrap are treated annually in Germany, the supply being
drawn from England, France, and Switzerland, besides from domestic
sources.
C. D. Brindley J has patented a process for recovering tin from
scrap, which consists in heating the scrap in an oven upon stepped,
inclined, and perforated plates, to which a jigging movement is imparted
by suitable machinery. In passing down the steps the solder melts
and flows through the perforations, and is collected from below. At
the bottom of the steps the scrap passes into a hopper, and thence into
a chamber, in which it is cut into strips by an arrangement of mechani-
cally-worked steel blades. After cleansing and dissolving off the tin
* " The Mining Industry," 1903.
t English Patent, No. 16,377, July 24, 1903.
X English Patent, No. 8,693, April 15, 1902.
250 TIN DEPOSITS OF THE WORLD.
or zinc coating by a suitable acid, the shearings are moistened with a
solution of an acid or mineral salt and exposed in heaps to the air.
When oxidised the mass is ground, and the ferric hydroxide is calcined
to form a pigment.
The Alkali Act of 1892 applies to tin mines where ores containing
arsenic are being roasted ; the exact proportion of arsenical fumes that
may be given off depends on circumstances. The Act is administered
by inspectors under the Local Government Board.
( 251 )
CHAPTER XX.
STATISTICS OF TIN PRODUCTION.
Tin mining must continue to be a progressive industry to keep up with
the demand for the metal. Very few new tinfields of any magnitude
have been discovered in the last ten years, whilst the easily-worked
alluvial deposits are everywhere being rapidly depleted, and what ia
left is costing more to win ; consequently, unless large and unforeseen
discoveries are made in Africa, north of the Malay Peninsula, or else-
where, there seems a reasonable chance of tin maintaining its present
price, with a tendency to increase.
It has been stated that high prices must react unfavourably upon the
uses of tin, but the experience of the last, few years has disproved that
idea, as the markets have (at the higher price of the metal) shown
that its consumption is quite equal to the increase of output. One
reason of this may be found in the fact that the great variety of manu-
factures into the production of which tin enters to some small degree,
but which aggregate the great bulk of the consumption, are conse-
quently much less adver^Bly affected by high prices than any individual
industry the product of which requires any considerable amount of the
metal, and this broadening of the field of industrial application is a
most satisfactory feature. Furthermore, tin once used is rarely re-
coverable in any large quantity, and is therefore a wasting commodity.
Various patented processes are in operation for the recovery of tin
from scraps, the most important works being situated in Germany, and
America ; and although it is impossible to get exact figures, the
recovery at present is a slow and costly one — but the cheapening of
these methods may lead in future to a new and disturbing element in
the tin market.
The treatment of new tin scrap, known as " detinning," has become
of considerable importance in the United States, and at least ten com-
panies were actively engaged in this special branch of the industry
during the year 1906. The average yield from tin scrap is approxi-
mately two per cent, of metallic tin. In addition, a large number of
small concerns in the principal cities recover the tin from old tin cans
and similar material by a smelting treatment in a furnace, the tin being
obtained in the form of solder, which is either used as a basis for
making new solder, or is treated chemically to yield metallic tin or tin
252 TIN DEPOSITS OF THE WORLD.
salts. The residue of scrap iron is generally utilized in the manufacture
of sash weights and other castings of inferior quality of iron.
The factor that must control the tin market to a very large extent
is the price at which it pays the tin mines of the Malay Peninsula to
continue producing the metal, and that at present is computed to be
£160 a ton for metallic tin.
Lode mining in the Malay Peninsula may be regarded as in its
infancy, and many years must elapse before the output from this source
can become a factor in the tin market.
With regard to the new tinfields lately discovered in Africa and
Alaska, it is too early to make a correct forecast of their future, but
from the reports furnished of the size and nature of these deposits, it
seems, in the opinion of the writer, a safe deduction to make, that many
years must elapse before these fields can become a real factor in the
tin market ; and although it is proverbially unsafe to prophesy, still the
inference to be drawn is that the price of tin cannot fall much below
£160 a ton, and it is felt that this inference is a fair and safe one, as
very little below that market price would cause many mines to close
down, and thus materially decrease the output.
The rise in price has also caused a search for a substitute for tin
in the manufactures. The possible use of such substitutes is well
summed up by L. Parry* in an excellent article, from which the follow-
ing quotations are made : —
" The diminution in the price of aluminum, the practically limitless
supply of raw material, and the physical properties of the metal are
facts which must at once appeal to the technical imagination, and point
to this — the most abundant of the metallic elements — as a possible
substitute for tin. At the same time it is not the only metal which has
to be considered in this connection.
"The world's annual production of tin is now about 91,000 tons
(long), and the principal uses to which the metal is applied are as
follows :
" A, The manufacture of tin plates. Tin plate holds from 2 to 3 per
cent, of tin. Two samples recently assayed by the writer contained
2*65 per cent, (thin piece) and 3 per cent, (thick piece), respectively.
The tin-plate production of South Wales is probably about 12,000,000
to 13,000,000 boxes, and that of the United States of America about
the same. Germany is probably the next largest producer, with about
1,000,000 boxes, or, say, 1,350,000 tons, for the world's production.
The tin in tin-plate is stated on good authority to run about 2J pounds
per hundredweight on output, or about 2 per cent., which means that
about 27,000 tons of metal are consumed for this purpose.
" B. The manufacture of machine bronzes and brasses, which in all
probability accounts for the greater proportion of the world's con-
sumption.
" C. The manufacture of various white alloys, such as solder, type
* Substitutes for tin : " Mining Journal," London, vol. 79, June 2 1906,
p. 728,
STATISTICS OF TIN PRODUCTION. 253
metal, pewter, Britannia metal, white bearing metals, to mention the
more important. Of these we would particularly direct attention to the
ever-increasing consumption of white bearing metals, or so-called anti-
friction metals, which contain all percentages of tin up to 90 per cent.,
and which, we might incidentally add, all hold 5 to 20 per cent,
antimony as an essential constituent — a point which may have some
bearing on the increased price of antimony. Of other white alloys we
have capsule metal, tea lead, tinfoil, electric fuse metal, accumulation
metal, metallic packing, fusible alloys, and the various white alloys
holding tin which are used for making ornaments and toys.
" D. Ornamental bronzes and gold and silver-plated white metals.
" E. Tin crystals, tin oxide, etc. A considerable amount of stannous
chloride (tin crystals) is consumed in various branches of textile
industry. Tin oxide is the principal constituent of many polishing
powders.
" A. With regard to tin-plate there is very little doubt that many of
the uses to which it is applied could be quite well fulfilled by aluminum or
galvanized iron, or, assuming the manufacture of such a material to be
a practicable proposition, by aluminum plate — that is, iron coated with
aluminum. The price of aluminum is now about that of tin and about
fourteen times that of tin-plate, and as the specific gravity of aluminum
is, roughly, one-third that of tin plate, the cost of aluminum sheet
would be about four and a-half times (Jx 14) that of tin plate of the
same thickness. A rise in the price of tin does not, of course, affect
very greatly the price of tin plate ; thus on January 6 tin plates
20 by 14 were quoted at 13s. 3d. per box, and on May 19 at 14s., an
increase of 9d. per hundredweight, or 15s. £0*75 per ton. We should
note that the price of steel bars had meanwhile dropped from £5 5s. to
£5. The price of tin on January 6 was £163, and on May 19 £194,
an increase of about £30 a ton. If we assume, for the sake of
argument, that there is 3 per cent, of tin in tin plate, the increased cost
of producing plates would be 3 per cent, by £30 — £*9 per ton, which
agrees pretty closely with the actual increase. An increase of £33 in
the price of tin means an increase in the cost of producing plates £1 per
ton, or Is. only per hundredweight. It is obvious from these figures
that a very large increase in the price of tin can have practically no
influence in diminishing the relative cost of aluminum sheet as against
that of tin plate ; with aluminum and tin at the same price, there is a
margin of £50 or £60 between the cost of equal bulks of the two
materials. Thus before aluminum sheet can hope to compete with
tin plate in the matter of price, one or both of two things must
happen — namely (a), an undreamt-of increase in the price of tin,
(b) a considerable lowering in the price of aluminum — a point to which
very considerable attention is being paid — the matter is very different ;
the cost of tin and aluminum being about the same, there might
easily be very little difference in the cost of producing the two
kinds of plate, and that difference might, as far as we know, be on
either one side or the other, though it would seem probable that the
cost of producing aluminum plate would necessarily be greater, owing
254 TIN DEPOSITS OF THE WORLD
to the higher melting point of aluminum and its ready oxidizability.
However, a rise of £20 or £30 a ton in the price of tin might then be
sufficient to turn the scale in favour of aluminum plate, other things
being the same. As is well known, aluminum is sufficiently tenacious
and malleable to replace tin plate, resists atmospheric influences well,
and, whether as plate or sheet, could be employed in the manufacture
of many domestic utensils and vessels used for containing food stuffs,
tobacco, etc. There cannot be much objection (apart, of course, from
cost) to its use in the case of such things as tea, coffee, cocoa, biscuits,
tobacco ; but in the case of preserved fruits, meat, and vegetables the
objection has been made that aluminum is attacked by organic acids.
This is a very important point, and one upon which there is much
conflict of opinion. It would seem that the liability of aluminum to
attack by fruit acids depend largely on its purity. In any case, we
must remember that the aluminum industry is in its infancy, that the
power of resistance of the metal to organic acids is a matter which
requires investigating, and that we can scarcely condemn its use
in such connection on the strength of the scanty knowledge we
possess.
" B. Machine bronzes and brasses may contain up to 5 per cent, tin,
according to the purposes for which they are required. As the world's
annual output of copper is now about 800,000 tons, and that a very
large proportion of this is employed in the manufacture of machine
bronzes and brasses, we see at once that this must mean a correspond-
ingly large consumption of tin. Many of the essential physical proper-
ties of tin-copper or tin-copper-zinc alloys may be obtained by the
partial or complete substitution of tin by aluminum, manganese, nickel,
or iron, though it would, perhaps, be incorrect to say that such an effect
could always be produced, or that such alloys would be invariably
cheaper. The object of successful brass founding is the production of
a suitable alloy at a profit. If, for instance, the price of tin, aluminum,
and nickel happened to be about the same, and it was found possible to
obtain the properties required in a gun metal holding 90 of copper and
10 of tin by adding 1 or 2 per cent, each of aluminum, nickel, and tin
to a copper-zinc base, it would certainly pay to do so. A rise in the
price of tin should stimulate research in the direction of such combi-
nations. It is an unfortunate fact, however, that the English brass
founder is disinclined to spend money on trained technical research, as
he has not yet discovered that it would pay him to do so. A large
brass founder (English, of course) once expressed to the writer his
opinion that a chemical laboratory was a waste of money in a foundry.
" The aluminum bronzes and brasses are a most important class of
alloys, and will be produced in much larger quantities as the price of
tin increases, or that of aluminum declines.
" C. Of the important white metals we may say at once that solder
and type are required on account of such special and definite combi-
nations of physical properties that their replacement by other metals to
any appreciable extent is quite improbable. With regard to white
bearing metals, again the tin which is used in their manufacture confers
STATISTICS OF TIN PRODUCTION. 255
physical properties upon them which can scarcely be otherwise obtained,
so that the consumption of tin in their manufacture is likely to increase
rather than to diminish.
" D. With regard to ornamental bronzes it is difficult to speak with
any degree of certainty. The use of tin, however, is not an absolute
necessity, and its consumption for the purpose has been diminishing for
some time. On the other hand, an increased amount of tin is probably
now used in the manufacture of white-metal ornaments — e,g,^ in the
case of white bronzes.
" Many white-metal combinations are employed in making ornaments,
and it is probable that the demand with regard to quality readily
accommodates itself to the supply. The quality of such goods probably
varies far more than the price. If tin keeps up in price for a year or
two it will probably be found that the percentage of tin in white-metal
ornaments will diminish considerably. With regard to white metals
used as bases for electro-plating with gold and silver, it has already
been found possible to use aluminum. The processes are still in their
infancy, but no doubt the use of aluminum for this purpose will become
more and more common."
The past year of 1906 has been a record one for tin, whether from
the point of view of production, price, or interest. At the same time,
there have been no new developments of any importance during the
year, and the general position appears similar to that at the end of
1905. Perhaps the most noticeable feature of the year is the decline
in the production of the Federated Malay States, in spite of the much
higher price averaged during the year, £180 12s. 9d. against £143 2s. Id.
per ton. In the Straits the price averaged about 19 dollars a pikul
better, as compared with a rise of a little over 4 dollars during 1905.
In the Dutch Indies the sales from Banca decreased from 9,960 tons
in 1905 to 9,298 tons in 1906. Production may have reached 1 1 ,000 tons.
Of Billiton there is not very much information. The sales during the
past year were reported at about 1,950 tons.
In Siam there is not much increase, and in regard to Siamese Malaya
probably the same causes which are operating to keep down the output
of the Federated Malay States will be experienced higher up the
country.
The next most important source of production is South America.
The Bolivian yield has been variously estimated. Dealing only with
exports they show that the ore exported amounted to 17,627 tons,
which at 60 per cent, gives us 10,574 tons of metal against 15,139 tons
ore, equal to 9,083 tous metal last year. The metal imports from
Bolivia are not shown separately, but as shipments other than those
from the Straits and Australia, of which in past years Bolivia has
claimed about half, show an increase of only 600 tons, 1,700 tons will
probably cover Bolivian metal shipments to England ; thus the total
would be some 12,274 tons to this country. The " Monatliche Nach-
weise uber den Auswartigen Handel Deutschlands " shows no shipments
to Germany from South America from March to November. On the
other hand, the imports of tin-ore amounted to no less than 13,000 tons.
256 TIN DEPOSITS OF THE WORLD.
which yielded 8,000 tons of pure metallic tin, and the exports of tin
from Germany amounted to 4,320, against 2,940 in 1905.
Australia has undoubtedly had a good year. The latest Government
figures I have been able to obtain by the courtesy of the various Agent s-
General are the following, calculated from values given at £180 a
ton : —
New South Wales (9 months), 1906- - - 1,256 tons.
Queensland (9 months) ,. - - - 1,985 „
Tasmania (6 months) ^^ - - - 1,357 „
West Australia (8 months) „ - - - 512 „
Averaging the remaining months on previous yield, the returns would
]3e .
1906. 1905.
New South Wales - - 1,675 tons. 1,215 tons.
Queensland - - - 2,647 „ 2,080 „
Tasmania - - - - 2,714 „ 2,536 „
West Australia - - - 768 „ 607 „
7,804 tons. 6,438 tons.
These figures are, of course, far from exact, but, as will be seen, they
give an increase of nearly 1,400 tons. Finally there are the increased
shipments from other countries, amounting to some 300 tons as metal
and 750 tons as ore. Of this amount, however, probably at least half
has been already included under Australia. We may allow, therefore,
600 tons under this head. The result works out, therefore : —
Decrease.
- 2,370
Increase.
]
Banca
Billiton
Bolivia
Australia -
Sundries -
2,350
500
2,000
1,400
600
Malay States
Total Increase
„ Decrease
6,850
2,370
Increase - - 4,480
That is to say, that last year production increased about 4,500 tons.
Taking the output in 1905 at 90,000 tons, the increase was 5 J percent.
The average increase in the production of tin from 1884 to 1903 was
5*11 per cent., so that the above result seems quite normal. On the
other hand, consumption last year was no doubt exceptional, as the
year was a record in the consumption of iron, copper, etc., to the use of
which tin bears a fairly constant proportion. Under the circumstances,
therefore, I can see nothing abnormal in the present prices, and, short
of a great decline in business, would expect to see something of the
kind averaging for the year ; though, of course, serious labour scarcity
in the East or Bolivia might cause trouble. On the whole, supplies are
on a good broad basis, adverse to marked fluctuations.
STATISTICS OF TIN PRODUCTION.
257
Economies in the use of tin are not unlikely to be introduced, and
it is expected that the quantity required during 1907 will be probably
over 36,000 tons for America. European consumption may be expected
to increase, after having been stationary for some time, and thus the
course of prices would seem to depend very much upon the quantity
to be produced in the Straits Settlements.
The consumption of tin produced is approximately as follows ;
this is compiled from official returns: —
United States -
Great Britain - -
Germany - - - „
France, Italy, Spain, Russia „
Eastern Europe and South 1
America J "
Eastern Asia - - - ,?
Total consumption
Taking 40*6 per cent, of output.
„ 16-8 „
„ 15-7
18-9
4-5
3-5
100-0
Comparative Table Showing the Total Visible Supply op
Tin at the End of Each Month.
In Long Tods.
19C6.
1906.
1904.
1903.
1902.
January -
16,115
1^,645
17,115
17,679
18,351
February
14,261
14,911
16,450
16,294
17,043
March -
12,748
14,592
15,662
19,497
18,131
April -
11,959
13,063
13,695
15,978
15,596
May - - -
13,520
12,967
14,609
16,463
17,018
June
12,590
11,938
13,780
15,107
15,897
July
13,013
12,270
13,818
16,507
16,809
August -
12,295
12,572
12,480
16,544
16,293
September
13,235
14,508
13,159
17,249
18,025
October -
11,778
12,812
12,194
15,515
16,053
November
12,825
13,174
14,412
15,195
18,346
December
13,320
13,451
14,768
14,274
16,769
^58
tin deposits of the world.
Statistics op Tin.*
straits and Australian, Bpot . . . .
— - n n landing and in transit -
Straits, afloat
Australian, afloat
Banca, on Warrants -
Billiton, spot
ll „ afloat -
Straits, spot in Holland
„ afloat to Continent
Total afloat for United States
Bstimated Stock in America
30th Nov.
1 3l8t Deo.
30th Dec.
31st Dec.
1906.
1906.
1905.
j 1904.
Tons.
Tons.
Tons.
Tons.
1,104
1,506
2.266
3.498
232
976
1,184
1,588
3,100
3,600
3,650
3,225
749
733
6,714
890
766
' 6,186
7,890
9,067
1,857
794
962
767
—
—
43
10
183
183
180
270
364
182
465
100
726
8,014
_620_
8,393
700
800
10,230
11,014
3,360
3,085
2,876
3,425
1,461
1,842
601
959
Total
Prices of Straits and Australian
Deliveries daring the month, in London -
n r> t, Holland
Shipments the month Dec. 1906 from Straits to London
,< ft « Straits to America
„ f, M Straits to Continent
„ „ Australia to London
London and Holland to America
- 3,600 tons.
- 1.136 „
- 615 „
6,260 tons,
726
1,781 „
During
12 months
ending
During
12 months
ending
31st Dec. 1906. 30th Dec.1906.
During
12 months
ending
31st Dec. 1904.
Shipments from Straits to London -
., „ Straits to Continent -
„ „ Straits to America -
„ M Straits to Europe and
America - - '
n M Australia to London
„ M Australia to America, &o.
Deliveries of Tin in London
„ „ London and Hol-
land
„ „ America - - ;
„ „ London, Holland,
France & n.S. -
36,110
7,563
13,663
57,226
5,361
1,311
14,484
26,988
37,700
74,614
33,773
8,151
15,136
67,059
4,466
856
14,876
28,726
37,700
76,420
Average Price Straits Tin for Cash - , £180 128.9d. £143 2*. Id. £126 13*. lid. £127 4«. Id. \ £120 14». 7rf.
35,840
7,346
14,444
67,630
4,248
14,127
30,271
35,900
76,411
During
12 months
ending
31st Dec. 1903.
28,710
6,448
17,013
62,171
4,157
16,301
30,420
37,500
76,156
During
12 months
ending
31st Dec. 1902.
28,925
6,840
16,225
51,990
3,166
50
14,806
,"10,944
36,930
77.046
Banca in Trading Company's hands, 1,371 tons.
PaiCBS : Straits and Australian spot
English Common ingots •
Banca - - - -
SUPPLY.
Straits
Aastralian
Billiton
Banca
£ s. d. £ t. d.
193 10 I Three months - - - - 194 10 per ton.
194 I Refined 197 „
195 I Billiton —
DECEMBER, 1906. CONSUMPTION.
5,250 tons. London Deliveries - - - - 897 tons.
725 „ Dutch 968 „
183 M American 2,800 „
„ Straits, Continental Ports - - 815 „
Billiton 183 „
6,168 „ 5,663 „
Messrs. RIOARD & PREIWALD give the VISIBLE supply of Tin on 3l8t December as 13,118 tons,
against 12,807 tons on 30th November, and 13,601 tons a year ago. Supplies for the month total 6,064 tons,
against 6,855 tons for November, and 5,554 tons a year ago. Deliveries for same period were 6,753 tons, as
against 5,942 tons for November, and 4,990 tons last year. BANOA and/or BILLITON SALES for the month
were: Billiton, 184 tons, as against 1,769 for November, and 124 tons a year ago. Banca in Trading
Companv'8 hand? December 1906. 1.360 tons : December 1906, 1.432 tons.
* *' Mining Journal," January, 1907.
STATISTICS OF TIN PRODUCTION.
259
Tin Production of Bolivia.*
The amount of tin exported from Bolivia during the year 1904 was as follows :
Quantity.
La Paz 13,427-99 Quintals.f
Oruro 260,174-11
Potosi 120,894-65
Uyuni 17,126*95
Colquechaca 23,735*90
Tupiza 20,620*07
Total - - - - 455,979*67
Representing an official value of £1,275,944.
Export op Tin for the First Six Months op 1906.
Customs Houses.
La Paz - - - -
Oruru - -
Uyuni - - - -
Tupiza - - . -
Becaudadora de Potosi -
Becaudadora de Colquechaca
Value. I Duty.
Total
639,764*32
8,502,055*34
814,291*08
1,910,104*00
3,751,399*82
335,894*30
15,953,508*86
Bfl.
639,764*32
8,502,055*34
814,291*08
1,910,10400
3,751,399*82
335,894*30 |
Bs.
32,188-98
412,548*76
41,534*69
92,304*25
170,606*98
16,101*08
15,953,508*86 | 765,284*74
The average of Straits tin, which governs the price in Europe, was for the first
six months of the present year £173 10*. per tonne, which corresponds for Bolivian
ores averaging 60 per cent, to £98 10«. per tonne. Taking exchange at |, and
deducting expenses in Europe, there is a net yield of one boliviano per kilo. —
[Signed] V. Tarfon, Inspector-General of Customs Houses, La Paz, 3rd June, 1906.
Production op Tin in Bolivia.!
Barilla.
Metric Cwts. of 100 kilos.
Metallio Tin.
Official Value in
Bolivia.
1 Tons.
1 Tons.
1 Bs.
1897
37,495 = 3,691
2,215
2,986,500.00
1898
43,960 = 4,327
2,596
3,405,000.00
1899
92,794 = 9,134
6,480
5,730,950.00
1900
162,342 = 15,088
1 9,053
1 8,579,539.00
1901
219,159 = 21,573
12,943
1 9,380,714.00
1902
176,088 = 17,340
10,404
1 8,782,703.00
1903
221,314 = 21,785
13,071
11,830,073.87
1904
206,919 = 20,369
12,221
1 9,191,701.51
1905
269,120 = 26,490
15.894
1 13,180,614.00
1906 (approx.) ..
. 1 284,444 = 28,000
16,800
1 34,490,000.00
Output op Barrilla or Tin Concentrates in Bolivia in 1905,
BY Districts.§
Long tons.
Oruro 15,180
Chorolque Potosi, January- June - - - 3,500
Huanuni -------- 460
Panza 200
Total - - - - 19,340
• From Mr. Consul Harrison's Report, dated La Paz, March 22, 1905, vide Mining Journal^
June 10, 1906, p. 627. t Of 100 lbs.
t " Mining Journal," April 20, 1907, p. 543 .
3 The exports are given by Mr. C. Mayer as 13,328 short tons for each year. Mr. J. Ramsay Smith,
British Vice-Consul at Oruro, gives the above figures of production of tin in Bolivia for 1905.
R 2
260 TIN DEPOSITS OP THE WORLD.
Tin Exports of Federated Malay States.
states.
Perak
Selangor -
Negri- Sembilan
Penang - -
Total Piculs
Metric Tons
1901.
385,060
302,570
75,230
26,310
789,170
47,713
.190^.
405,870
278,360
73.520
23,120
780,870
47,211
1903.
436,296
284,592
85,461
25,317
831,666
50,254
Total
Metric Tons
t P6rak -
Selangor -
Negri Sembilan
Pahang -
1904.
1905.
Pikul.*
446,782
289,867
85,133
34,879
1906.
-
Pikul.*
450,670
304,701
85,688
28,068
435,909
268.624
77,766
34,488
-
869,127
t 57,942
51,790
856,661
J 57,111
51,793
816,786
148.618
Federated Malay States Tin Output in Pikuls.
January -
February -
March
April
May
June
July
August -
September
October -
November
December
Pikuls.
71,332
57,425
64,999
68,073
77,872
65,216
65,247
73.919
66,281
75,121
67,614
65,774
1905.
Pikuls.
84,245
56,718
71,579
62,975
71,514
73,035
77,085
74,106
65,958
71,203
70,661
78,606
Total, 12 months
816,786
856,660
Pikuls.
72,816
63,009
63,591
63,473
64,106
71,422
71,949
83,427
78,106
75,878
78,217
76,282
869,128
* Pikuls : pikul = 138| pounds.
t ** Mining Journal" (London), Vol. 79, No. 3682, March 17, 1906, p. 362.
; Short tons.
statistics of tin production,
Monthly Returns from Straits Settlements.*
261
—
1901
1902
1903
1904
1905
1906
January - - -
3,825
4,035
4,740
4,950
5,233
5,998
February - - -
3,980
4,315
3,440
4,716
4,527
4,399
March - - -
3,900
4,645
5,395
3,476
4,169
3,860
April -
4,250
3,995
3,220
5,450
4,613
4,898
May - - -
4,170
4,160
5,470
4,805
4,661
5,299
June - - - -
4,320
4,970
4,345
5,138
5,078
4,623
July - - - -
4,160
3,670
4,660
4,442
4,158
4,636
August
4,490
5,180
5,160
4,732
5,752
4,965
September -
4,680
4,830
4,465
4,319
4,993
4,126
October
3,810
3,835
4,140
4,993
3,915
5,210
November -
4,820
4,340
3,760
5,400
4,933
4,982
December -
4,100
3,770
3,190
5,142
4,897
4,218
Tin Production of Tasmania.
Return showing the Quantity and Value of Tin exported from Tas-
mania during the years 1880, 1881, 1882, 1883, 1884, 1885, 1886,
1887, 1888, 1889, 1890, 1891, 1892, 1893, 1894, 1895, 1896,
1897, 1898, 1899, 1900, 1901, 1902, 1903, 1904 and 1905, com-
piled from Customs Returns only.
Year.
Quantity.
I
1880
1881
1882'
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
190?
1903
1904
1905
Tons.
£
3954
341,736
4124
375,775
3670
361,046
4122
376,446
3707
301,423
4242
357,587
3776
363,364
3607J
409,853
3775J
426,321
3764
344,941
3209}
296,368
3235
291,715
3174
290,083
3128i
260,219
2934
198,298
27261
167,461
2700
159,036
2423i
149,994
1972
142,046
2239}
278,323
2029
269,8bH
1789i:
212,542
1958: ■
237,8.28
2376^
300,098
2171
255,228.
3891i
362,670
11,499|^
7,530,234
' Returns in tons of 2,240 lbs.
262
TIN DEPOSITS OF THE WORLD.
Tin Production of New South Wales.
The following Table shows the quantity arid value of Tin exported from
this State since the opening of the Tin Fields in 1 872 to the end of 1903 : —
Year.
Ingots.
Ore.
Total Value.
Quanti
by.
Owt.
Value.
d.
Quantity.
Value
i.
Tons
£
s.
Tons.
Cwt.
£
s.
d.
£ i. d.
1872
47
6,482
849
41,337
47,819
1873' -
911
107,795
3,660
226,641
834,436
1874
4,101
366.189
2,118
118,133
484,322
1875. -
6,068
476,168
2,022
86,143
561,311
1876
6,449
379,318
1,509
60,320
439,638
1877
7,230
477,952
824
30,688
508,640
1878
6,085
362,072
1,125
33,760
395,822
1879
5,107
2
343,076
813
16
29,274
372,349 C
1880 -
6,476
6
440,616
682
6
30,722
471,337
1881
7,590
174
686,611
609
6
37,492
724,003
1882
8,069
800,671
611
32,890
833,461
1883
8,680
I
802,867
446
4
21,685
824,552
1884
6,315
16
606,726
349
13
14,861
521,587
1886
4,667
18
390,468
634
18
26,168
416,626
1886
4,640
18
449,303
326
18
18,360
467,663
1887
4,669
8
609,009
291
13
16,411
625,420
1888
4,662
2
669,182
247
8
13,314
582,496
1889
4,408
13
403,111
241
15
12,060
416,171
1890 -
3,409
11
317,117
259
4
12,724
329,841
1891
2,941
5*
261,769
203
5
9,643
271,412
1892 -
3,263
301,541
239
2
12,673
314,114
1893
2,636
17
223,139
148
1
6,604
229,743
1894
2,611
5
179,446
190
7
7,762
•187,197
1895
2,199
11
136,080
77
4
2,543
138,623
1896
1,710
4
99,212
96
19
2.906
102,117
1897
1.140
13
70,128
14
2
660
70,688
1898
898
17
60,565
1
4
36
60,600
1899
821
15
98,138
4
16
290
98,428
1900 -
901
5
120,032
16
2
900
120,932
1901
656
8
76,851
10
17
464
77,316
1902
446
6
52,636
22
19
1,070
53,706
1903
751
19
96 463
646
14
29,430
124,893
1904
1,067
17
130,881
626
4
49,496
1«8,377
1905
804
6
112,166
714
14
61,640
173,806
Totals -
71,008
2
6,386,229
20,603
13
1,060,232
7,436,461
Includes tin refined from imported ores to the end of 1898.
New South Wales Government Report on Mining Industry.
The Production of Tin in Western Australia.
Year.
Tin Ore
Year.
Tin Ore
Estimated
Exported.
Value.
Exported.
Value.
Tons. Cwts. Qrs.
£ s.
d.
Tons. Owts. Qrs.
£ «. rf.
1889 -
5
300
1899 -
335
26,270
1890 -
67 10
6,400
1900 -
823
66,702
1891 -
204
10,300
1901 -
734
40,00U
1892 -
265 9 3
13,843
1902 -
620
37,783
1893 -
227 19
11,134
1903 -
817
55,890
1894 -
390 5
16,274
1904 -
864
58,817
1895 -
277 3
9,703
1905 -
1,079
86,840
1896 - '
137 5
96 11
4,338
3,275
,
^ 1
1897 -
1898 -
1
68 2 3
2,760
Total -
6,928 7 8
433,829
STATISTICS OP TIN PRODUCTION.
2(53
Tin Production op Queensland*
Tin Ore.
Tin Ore.
Tons.
Value.
Tons.
Value.
1872
1,407
109,816 1
1890
2,970
154,963
1873
8,93H
606,184 1
1891
2 236
116,387
1874
5,702
358,550 1
1892
2,389
123,098
1875
4,475
237,879 :
1893
2,434
106,953
1876
4,315
187,201
1894
2,871
102.277
1877
3.335
133,432
1895
2,114
68,133
1878
2,849
88,366
1896
1,554
49,018
1879
2,877
120,391
1897
1,203
37,509
1880
2,847
142,977
1898
1,025
36,502
1881
3,456
193,699
1899
1,308
77,302
1882
4,261
269.904
1900
1.123
74,041
1883
3,346
187,292
1901
1,661
93,723
1884
3,383
130,460
1902
2,085
116,171
1885
3,253
151,871
1903
3,708J
243,149
1886
3,153
162,124 ;
1904
3.923
270,276
1887
3,279
217,389 1
1905
3,945
297,454
1888
3,586
200,019
1889
3,033
156,406
Total -
104,044J
5,620,916
* Output and Value op Tin Ore (" Black Tin ") in the
United Kingdom from the Year 1873 to 1905.
Year.
Quantity.
' Value.
; ^
Year.
Quantity.
Value.
Tons.
Tons.
&
1873
14,885
1 1,056.835
1890
14,911
782,492
1874
14,039
788,310
1891
14,488
735,240
1875
13,995
735,606
1892
14,367
734,565
1876
13,688
600,923
1893
13,689
637,053
1877
14,142
572,763
1894
12,910
487,523
1878
15,045
530,737
1 1895
10,612
370,530
1879
14,665
586,608
; 1896
7,663
259,928
1880
13,738
673,142
1 1897
7,120
254,218
1881
12,898
, 697,444
1898
7,380
288,325
1882
14,045
1 805,847
1899
6,392
440,509
1883
14,469
735,189
1900
6,800
523,604
1884
15,117
1 669,254
1901
7,288
478,559
1885
14,376
662,390
1902
7,560
513,872
1886
14,232
780,302
1903
7,382
532,450
1887
14,189
878,831
1904
6,742
479,63r.
1888
14,370
894,665
1905
7,201
574,183
1889
13,809
729,213
* Government Mines Beport, 1905.
tin deposits op the world*
Tin Production op Banca.*
Tons.
1900-1901 12,335
1901-1902 10,400
1902-1903 10,400
1903-1904 12,438
1904-1906 - - - - - 7,700
1905-1906 8,832
The quantity of Banca tin sold and the average price per 50 kilos
at the six bi-monthly sales during 1905 was as follows : —
t Tons.
January sale
March
May
July
September
November
Total
57,400
46,500
47,183
45,995
45,987
45,802
1,979
1,603
1,627
1,586
1,586
1,679
9,960
Average Price.
Florins.
79
83i
83J
90|
881
96|
Tin Production op Billiton.
Tons.
Tons.
1^96-1897
4,479
1901-1902 -
, 4r,661
1897-1898
5,266
1902-1903 -
4,484
1898-1899
6,406
1903-1904 -
3,870
1899-1900
4,762
1904-1905 -
4,218
1900-1901
4,479
1905-1906 -
4^,462
* Official estimate.
t Official estimate long ton of 2,240 lbs. given.
STATISTICS OF TIN PRODUCTION.
265
Exports of Tin from the United Kingdom in the
Years 1905-1906.*
(Return by Board of Customs.)
Countries to which Exported.
BRITI8H.t
Quantity. Value.
Russia :
Northern Ports - - -
Southern Ports - - -
Sweden
Norway - - - _ .
Denmark - - -
Germany - - . - .
Netherlands - - . .
Belgium - - . -
France
Portugal, Azores, and Madeira -
Spain and the Canaries
Italy
Austria-Hungary
Greece
Bulgaria - . . . .
Boumania - - - - -
Turkey :
European • - . .
Asiatic ....
Egypt
British Possessions in S. Africa -
East Coast of Africa ...
British East Indies
China
New Zealand ....
British North America
United States of America :
On the Atlantic -
British West India Islands and
British Guiana •»
Foreign West Indies -
Mexico
Peru ------
Chili
Brazil - . . . .
Uruguay - - -
Argentine Republic . . .
Other Parts - . - .
Total Exports in 1905
Total in Preceding Year -
Tong.
898
500
401
119
78
844
141
126
758
398
487
95
97
44
45
25
108
132
215
93
7
170
11
13
440
1,287
5
20
16
10
56
137
26
287
34
5,864
£
126,585
'67,842
55,642
16,497
10,858
47,927
20,028
17,376
105,643
55,098
68,826
13,127
13,941
6,225
6,546
3,576
15,550
19,203
31,036
12,984
760
, 22,986
1,531
1,745
61,143
171,936
802
2,809
2,126
1,384
7,853
19,171
3,611
40,238
5,265
7,623 I 1,057,780
741,847
FOREIGN.
Quantity.
Tons.
675
121
4
33
1,609
4,242
46
110
11
377
26
33
21,802
3
48
7
1
29,155
27,225
Value.
£
95,972
17,227
590
4,425
224,724
608,582
5,278
15,357
1,483
53,516
3,489
4,124
700
154
3,076;718
458
6,391
1,014
183
4,120,385
3,430,280
* Government Mines Statistics, 1906.
t The figures under this heading include tin which had been imported from abroad,
but which was refined at the smelting. works in England, and was accordingly
declared by the exporters as British tin.
266
TIN DEPOSITS OF THE WORLD.
O
H
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O
OS
O
Q
525
Q
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STATISTICS OF TIN PRODUCTION.
267
United Kingdom Imports of Tin Ores, 1906.*
—
To November.
December.
Total for 12 months.
1
Tons.
Tous.
Tons.
Eussia
36
—
36
Sweden -
3
—
3
Germany -
567
26
593
Netherlands
249
2
251
Belgium -
106
2
108
France
544
78
622
Portugal -
56
1
57
Spain
168
27
195
Italy
32
3
35
Bolivia :
Peru
. 1
268
—
268
Chili -
1
16,309
976
17,285
Argentine
63
11
74
U.S.A. -
—
9
9
Canada -
6
—
6
Cape Good Hope
-1
121
12
133
Natal
. 1
1
1
11
—
11
Portuguese East Africa
" 1
304
13
319
Burmah -
1
1
-
1
Bengal -
2
—
2
Straits Settlements
_ 1
86
—
86
New South Wales
524
76
600
Victoria -
- j
10
—
10
Western Australia
1
2
—
2
Total -
19,478
1,236
20,714
* Specially compiled for The MiniTig Journah
268
tin deposits of the world.
Market Price of Tin.*
1
Total visible
1
Total visible
Year.
Highest.
Lowest.
Supply,
Year.
Highest.
Lowest.
Supply,
£
January 1.
,
January 1.
£
Tons.
' .
£
Tons.
1850
85
70
—
1879 -
96
59
18,269
1851
88
78
—
1880 ■
101
68
21,954
1852
98
77
—
1881 -
110
86
20,385
1853
125
97
—
1882 -
1 114
92
16,475
1854
126
105
—
1883 -
99
83
15,574
1855
130
104
—
1884 -
87
73
16,334
1856
143
126
—
1885 -
1 97
74
13,138
1857
150
95
4,118
1886 -
103
92
13,710
1858
125
100
5,474
1887 -
! 167
100
12,239
1859
142
125
4,690
1888 -
; 170t
75
18,226
1860
135
129
5,841
1889 -
1 100
88
14,802
1861
130
110
5,781
1890 -
104
88
13,693
1862
119
110
6,747
1891 -
94
89
13,050
1863
128
113
7,002
1892 .
103
88
12,435
1864
120
87
7,184
1893 -
95
74
14,606
1865
97
87
9,273
1894 -
74
61
14,316
1866
95
75
10,418
1895 -
1 69
59
27,787
1867
91
83
10,856
1896 -
; 61f
56
33,073
1868
109
87
9,115
1897 -
63J
58i
32,104
1869
140
108
7,834
1898 -
86f
63
29,616
1870
135
103
8,797
1899 -
I49i
92
22511
1871
157
123
7,742
1900 -
152
108
17,543
1872
160
130
6,151
1901 -
132
101
. 17,131
1873
148
114
6,846
1902 -
137
100
18,776
1874
121
87
8,289
1903 -
, 136J
1114
16,151
1875
96
76
10,704
1904 -
116f
13,948
1876
81
70
13,776
X905 -
1 166|
1291
15,398
1877
76
64
14,430
1906 -
215
161
13,606
1878
66
52ii
15,596
'
Mining Journal, London.
t Highest.
X Lowest.
WHITE
TIN :
BLACK
TIN:
WHITE
TINS
LONDON %.^^^^K
\k^k\l li£ORUTH LONDON
fioo __ i^l
lliLtt.^116f
2oo£
1Q6 i.
- ^ >i) dk ^ ii •*
196
y9z _ JE;
i9Z
^1
fee
foe
/eu
r r
/eo - s -
f06
160
/76 S'^i- -
/Oh.
/76
/72 till-
f02
irz
/68 __
WO
16&
/6A _
9B
16/4.
/6^
96
leo
/S6
9A
fS6
/S2
9Z
1S2
/A8
90
/A0
/AA .
SB
1UU
//*o _
86
/AO
/36 -
8A
136
/32 -
3£
152
/28 -
SO
120
/^A -
7&
1ZU
T6
120
2 /OOT ■ 7/*.
lie
/1Z
//2 IN 1
TTI 7z
( 269 )
CHAPTER XXI.
TIN SMELTING.
In this account of tia smelting, only the methods at present employed
are described. Strangle as it may appear, a considerable quantity of
metallic tin is still produced annually by the Chinese using their
primitive methods of smelting, of which a short description is given.
Otherwise by far the greater part of tin produced is still smelted in the
ordinary reverberatory furnace. Tin smelting has been successfully
carried on by means of blast furnaces, but the loss of tin is greater,
and this is the main consideration in treating a product worth over
£190 per ton ; also it is well to remember the axiom of Dr. Percy, ' The
end of all metallurgical operations is the balance sheet.^ Trials have
been made with gas furnaces without any marked success, but
undoubtedly there still exists room for improvements in tin smelting,
certainly one of the oldest and perhaps the most backward of present
metallurgical processes.
Tin Smelting in Cornwall.
The ordinary type of reverberatory furnace is in general use in
Cornwall, The dimensions of these furnaces are as follows : —
Bed 18 feet long, 10 feet to 12 feet wide, fire-bridge 6 feet long by
2 feet wide, 3 feet deep. The bed is made over a hollow arch, and this
together with fire-bridge, which is also hollow, is kept cool by a free
circulation of air.
The bed is carried on iron bars laid transversely upon these slabs of
slate, or fire-clay tiles are laid, which are again covered by a bed of
fire-clay, upon which again the true bed of the furnace is built, which
consists of first-class fire-bricks laid on end and well grouted in.
This bed lasts about three months and takes two days to renew.
On the ground level below the true bed is a floor of fire-bricks
which catch any tin which may have leaked through ; this floor slopes
towards an iron pan into which the tin is ladled. The bed itself slopes
all round to the tap-hole, in front of which is a cast-iron float, near
which is a refining kettle with a small independent fireplace ; opposite
the tap-hole is the charging door, and near the flue is the working door .
of the furnace, which has an iron roller to help in the use of the rakes,
rabbles, etc. Opposite to this working door the fire door is placed high
up ; this is kept practically closed by the coal when the furnace is in
operation, the fireplace being kept full almost to the level of the fire
bridge. Such furnace has a stack about 50 to 60 feet high fitted with a
damper. A furnace of this description can be built in Cornwall for
about £250 ; this estimate would include the stack and flues.
270 TIN DEPOSITS OF THE WORLD.
In building furnaces in Cornwall the work is done bjr the furnace
men. One man can build a furnace bed in two days, and a furnace can
be turned out and rebuilt in a week, it taking six hours to charge and
run it down to metal, each set of men smelting two charges of ore.
The charge consists of tin ore mixed with very fine culm from 15
to 20 per cent, according to the nature of ore treated. To this is added
a little slacked lime and small quantities of slag.
All these constituents are mixed very thoroughly and damped with
water. The charge is then placed in position in front of charging door,
when it is shovelled in and spread smoothly over the bed by means of a
rabble.
The doors are closed or well luted and the fire then put on.
The charge is well melted in about three hours, it is then rabbled
and allowed to settle so as to get the slag separated from the metal ;
this operation is repeated when necessary, and the slag drawn through
the working door ; if too thin it is thickened by a few shoYelsfull of
culm ; the top layer of slag is generally fairly clean.
The next lot of slag contains tin as prills, and is then crushed and
washed, the old beds of furnaces being treated in same manner.
The tapping of a furnace is as follows : — When the charge of ore
is seen to be properly smelted, which i? indicated by its complete
liquidity and the cessation of its working, i.e., giving off its combined
oxygen, the process of tapping the furnace is undertaken. The clay
stopping of the tap-hole is pierced by an iron bar, and the metal and
fluid slag are allowed to run out into the clay -lined basin called the float.
The slag quickly cools and sets on the surface of the still liquid metal,
and is as soon as convenient removed for further treatment in a slag
furnace, and the liquid tin is then ladled into moulds, the flat slabs of
tin so produced, weighing about 80 lb. and known as tappings are then
ready for refining. On the completion of the tapping process there is
still left on the bed of the furnace a considerable quantity of partially
consumed anthracite, which holds back a part of the slag and a certain
quantity of metallic tin ; this mixtore of anthracite, slag, and tin is
raked out through the working door, and there is generally sufficient
slag present to bind the whole into a solid mass which is ultimately
taken to a crusher or stamps ; the anthracite is removed by a dressing
process of stripping or huddling, and the slag and metal are separated
by jigging, the slag going to the slag furnace, and the metal, which is
generally of a hard character owing to the iron present, goes to a
smelting furnace for treatment by itself.
All Cornish ores, having gone through a process of fine stamping,
dressing and calcination, come to the smelting house with but little
silica or alumina, but invariably with a percentage of oxide of iron and
such other heavy metallic oxides as have not been removed in the
dressing process. In the Straits iron is added to clean the slags, which
appear always to have an excess of silica. At Mount Bischoff the
alluvial ores containing an excess of silica are advantageously smelted
with ores containing an excess of iron, but in Cornwall all the ores have
invariably iron in excess, and in consequence the Cornish smelter has
TIN SMELTING. 271
throughout his operations to contend with compounds of tin and iron,
known as hardhead. The usual methods of dealing with this alloy is
a calcination to effect an oxidation of the iron, followed by a smelting
process having for its object the slagging off of the iron and the
reduction of the tin. The process is a tedious one and undoubtedly a
good deal of tin is lost in the process.
In Cornwall two-ton furnaces have been adopted, and these can be
worked with four charges in the twenty-four hours.
The total number of men employed in the largest smelting works
was only sixteen hands for night and day work.
The men are not paid by the hour. There are two shifts of twelve
hours, from six in the morning to six in the evening, and from six at
night to six in the morning ; during the night when four furnaces were
at work with two charges in each, the labour of wheeling the charges
to the floors, tapping the furnaces, ladling out the metal, removing the
slags and everything else rested in five men.
Methods of Buying and Selling Tin Ores in Cornwall.
The cwt. of 115 lb. is adopted. The drafted allowance is not
a deduction from the weight of tin ore, but an allowance for the
weight of the sacks in which the tin ore is packed. There is no
deduction or allowance for moisture ; the ores are samples, assayed and
sold with their contained moisture. It would be better if the cwt. of
112 lb. were adopted and the ores were sold by dry weight, but the
ores are sold by public tender at a price ruled by the market value of
metallic tin.
There is no reliable published information as to Cornish smelters'
profits or to the loss in smelting, but as regards this last point it is
probable that with the best ores the loss in Cornwall is not appreciably
different to that experienced in the Straits, and that with poorer ores,
with a large excess of oxide of iron, the loss is somewhat heavy. To sum-
marize, the position in Cornwall, which is only satisfactory to the smelter,
and with the present revival in Cornish mining, it is to be hoped that
the sale of tin ore will be put on a modern footing, that a cwt. of tin
ore will be 1 12 lb. and that a satisfactory arrangement will be come to as
to allowance for bags and moisture. This in the writer's opinion would
be better in the interest of both the smelter and producer.
The Mount Bischoff Company (Tasmania),
Has erected smelting works at Launceston, the nearest large town
to the mine to which the ore is shipped from the mine from
Lun Bay ; these works also do the smelting for all the rest
of the mines in Tasmania at a uniform charge of £3 per ton. Mr.
George J. Latta, the smelting works manager, has published in
the Report of the Secretary of Mines for Tasmania the following
particulars : —
" From a smelter's point of view these ores are as a rule remarkably
pure, there being no impurities in them to prevent the metal being
272 TIN DEPOSITS OF THE WORLD.
refined up to market quality. The impurity in the Mount Bischoff ores
is principally iron, and that in the alluvial ores is silica, and it is a
mutual advantage to smelt both together, the iron in the former com-
bining with the silica in the latter to form slag. When alluvial ores
are smelted by themselves it is often necessary to add iron in some form.
" The furnaces used are of the reverberatory type, the draught being-
supplied by a chimney. A charge is made by mixing 50 cwt. of the
various ores with about 10 cwt. of small coal ; this is thrown into a hot
furnace, and the doors carefully closed to exclude air. The time taken
to completely reduce the charge is eight hours, during which time it is
subjected to several rabblings or mixings. When properly smelted the
metal sinks to the bottom of the furnace, and the slags or impurities
float on the top ; the metal is then tapped into a float, or brick -lined
vessel, and allowed to cool for some time, and the slags are skimmed out
and reserved for future treatment ; another charge is thrown in and the
operation repeated. The metal in the float is ladled into a large kettle,
where it is refined by sinking billets of green wood under the surface ;
the heat of the metal converts the moisture or sap of the wood into
steam, and causes the contents of the kettle to be violently agitated ;
this has the eflTect of releasing any entangled portions of oxide or dross,
which float to the surface and are skimmed off. Samples are taken at
various times, and, when sufficiently refined, the metal is ladled into
moulds. This metal assays 99*80 per cent.
" The slags from the ore vary in richness, according to the quality of
the ores smelted and the working of the furnace. These slags are
broken up and mixed with small coal and lime, and again. smelted, the
metal produced from them being very impure from the large amount of iron
present. The iron is got rid of by smelting with the next charge of ore.
" A few parcels of ore contain traces of arsenic and copper, and
sometimes lead, antimony, and zinc. These have to be treated
separately. When arsenic is present every trace must be got rid of by
roasting before smelting, otherwise it causes the metal to be hard, and
there are no means of eliminating it once it is alloyed with the tin.
" Metal is sent from the works in the form of ingots, weighing 75 lb. ;
this is for shipment to England. Smaller ingots are made for con-
sumption in the colonies.
"From the ore sent to the works for smelting for private people or
companies a deduction of 2 per cent, is made to cover loss in smelting ;
that is, for 20 cwt. of ore, at 72 per cent., 14 cwt. of metal, or 70
per cent., would be returned to them. This allowance is for ores of 70
per cent, or over ; when the quality falls below that a larger reduction
is made, as the loss in smelting increases rapidly as the ores get
poorer."
Chinese Method of Tin Ssielting.
A very primitive method was to dig a hole in clayey ground about
20 inches deep and 14 inches in diameter.
The blast used was produced by using two vertical hollow logs of
wood 6 feet 6 inches high and 8 inches in diameter. There was a wood
TIN SMELTING.
273
piston in such log, the two being worked alternately by a man, a bamboo
tube conveying the blast into the furnace. The molten metal was
collected at bottom of the hole and recast with small clay moulds.
The Chinese furnaces at present in use in the Malay Peninsula are
an improvement on the primitive methods described : —
* The Chinese used two forms of furnace, a draught furnace and a
blast-furnace ; their construction was similar, consisting of a short
cylindrical or slightly conical stack made of clay, kept in place by
bamboo poles and hoops ; the interior consisted of a crucible between
9 inches and 12 inches in diameter, cylindrical at the bottom for more
than a foot, with a conical stack 2 feet to 2 feet 6 inches high, opening
outwards to a diameter of about 2 feet or more at the top. There was
,g„^i^^^^~^ii»^t^ir
Fig. 38. Chinese Smelting Furnace.
a small tap-hole in front, and an opening at the back that admitted a
clay tuyere about IJ inches inside diameter, or in the other type of
furnace admitted a couple of short clay pipes about 3 inches in
diameter. The draught furnace was preferred, but could only be used
with first-rate charcoal. The furnace, fig. 38, "was a mass of clay with
bamboo stakes driven into the ground around it, and bamboo hoops
to hold it together. The actual furnace, or crucible, was at E ; A was
a moulded cylindrical clay tuyere between 5 inches and 6 inches in
diameter, 2J inches bore, and about 22 inches long. The bamboo
blast-pipe was shown at F, which conducted the blast from what was
practically a double-acting blowing cylinder made of a hollow tree-
trunk, 12J inches in diameter and 10 feet long, with a wooden piston
* " Trans. Inst, of Civil Engineers," vol. cxxv.
"274 TIN DEPOSITS OF THE WORLD.
packed with leaves or feathers. One man mostly did the blowing,
more rarely two. The blast was irregukr and . intermittent, and the
average speed probably did not exceed ten strokes per minute. The
front of the hearth was arched, and the crucible itself was closed in
front, when at work, by a lump of clay, C, through which a small tap-
hole, B, about J inch in diameter, was kept open by means of a stick,
or at times an iron rod. The tin trickled into a hole, D, in the ground
lined with clay — the Chinese equivalent of the 'flote.' The molten
tin was kept covered with burning charcoal, and from time to time was
ladled out and cast into pigs by means of a sand mould, a wooden
block being used as a pattern. Each pig weighed 60 kati (80 lb.).
The exact consumption of fuel was difficult to ascertain, and varied
with the quality of the charcoal within wide limits. Thus about
60 per cent, of tin was obtained from ore that probably contained 68 per
cent, or 69 per cent., together with a small amount of very rich slag.
This slag was pounded under a rough tilt hammer, washed to extract
the prills of metal, and then smelted in small furnaces about 2 feet
6 inches or 3 feet high, these poundings and smeltings being repeated
between four and six times before the slag was thrown away as worth-
less. Now, in watching an operation in one of these furnaces, the top
would be found to be comparatively cold ; the tap-hole was so cold that
even the fusible iron and tin silicate were pasty, and would not run
freely, all the heat being in a small reduction zone about the tuyeres.
There were three methods of reduction : — (1) Direct reduction of the
tin oxide by carbon or perhaps by carbonic-oxide in the region of the
tuyeres. (2) There was always some magnetite with the ore, which
would be reduced to metallic iron in the furnace just above the tuyeres,
and this would in its turn reduce the silicate of tin. (3) It was most
probable that the nitrogen of the atmosphere, in the presence of the
alkaline carbonates in charcoal-ash, would combine with some carbon to
form cyanide of potassium, which, volatilised by the heat of the tuyere
zone, would condense somewhat higher up and would reduce the ore at
a very low temperature. It was well known that alkaline cyanides
were formed under perfectly analogous circumstances in the blast
furnace, and the readiness with which such cyanides reduced oxide of
tin was equally well known. Probably all three of these reactions
came into play in the Chinese method of tin-smelting, and it is im-
probable that water-gas played any part at all in the reaction.
"Tin-Smelting at Pulo Brani, Singapore."*
To the Straits Trading Company belongs the credit of being the first
European company to compete successfully against the Chinese in tin-
smelting. In 1885-6, one or two agencies were established in the
States of Selangor and Sungei Ujong. It was decided to build works
in or near Singapore, on Pulo Brani, an island lying south of Singapore
Island and west of the town. It is reached from the business part of
* Extracts from " Trans. Inst, Civil Engineers," vol. cxxv. McKillop & Ellis.
TIN SMELTING. 275
the town by a drive of 3 miles and a ferry of about J mile. The island
is about 250 acres in extent ; and the channels by which ships approach
it are fairly easy to an experienced pilot. The chimneys of the works
form a conspicuous feature of the view on entering the harbour from the
west, and will have been noticed by anyone who has visited the capital
of the Straits Settlements in the last eight years. Smelting at these
new works was begun in December, 1887, with one 2-ton furnace, and
has continued ever since. The works rapidly increased in extent, and
at the end of five years practically covered 8 acres. They now consist
of twelve 4-ton furnaces with accessory plant.
General Arrangement of the Works, — Everything, with the excep-
tion of the European quarters and part of the refinery, is on one level —
6 feet to 8 feet above high-water. The ground sloped naturally to the
sea-front, and a good deal of cutting and filling has been done at various
times tp level the place. The high ground at the back, 20 feet to
25 feet above the works level, is reserved for European bungalows.
Coal-ships and local steamers lie alongside the wharf, and lighters dis-
charge ore, etc., from the dock direct into the ore-room.
The sheds covering the furnaces, machinery, and coal-sheds have
light iron roofs covered with galvanized iron and carried on iron
columns. The store and mixing-room is a brick building about 250 feet
long by 50 feet wide. The refinery and metal store are similarly built.
The bungalows for Europeans are of wood, surrounded with wide
verandahs and carried on brick piers. The huts for the coolies are
light wooden buildings carried* on wooden posts, covered with the thatch
of the attap palm — a style of building suitable to the climate and to the
habits of the natives. The blacksmiths', carpenters', and other work-
shops are wooden sheds covered with attap. The superior native
servants, mostly clerks and weighmen, have each a brick house, two
storeys high, built in the local style with an air-shaft in the centre.
Buying and Handling Ore, — By far the greater quantity of ore
landed on the wharf of the works is bought by the Company's officers
at various agencies in the native States. Both at the agencies and at
the works the value of the ore is determined by cyanide assay. If it
contains much impurity, the sample is first boiled in aqua regia, and is
occasionally vanned. From the appearance and hardness of the assay
button obtained, no less than from its weight, the agent fixes the price
he will offer. When bought, the ore is sometimes further dressed at
the agencies by various devices. The comparatively small quantity to
be treated renders any other than manual power impracticable. Hand-
jigging and sluicing are the methods usually adopted, yielding ore of
high quality and rich tailings. Fortunately natives can be found to
work these tailings over again with infinite pains in a " dulang," or
wooden dish similar to the Australian miner's dish, but larger and not
so deep. The ore is afterwards dried, packed in canvas or jute bags,
labelled, and sent down with a guard to the nearest port, where it is
shipped direct to Pulo Brani. The ore, when landed, is carried to the
store, weighed and stacked under cover by coolies, under the supervision
s 2
276 TIN DEPOSITS OF THE WORLD.
of a weighing-clerk. The assay er then samples and assays each parcel ,
and his report determines the subsequent treatment. Those lots which
need to be roasted are stored in the roasting-house, while the clean ore
is emptied into bins in the mixing-rooms. The cost of the bags is a
very serious item. When emptied of ore they are taken to a separate
room, cleaned, dried, repaired, packed into bundles of one hundred each,,
and sent back to the agents.
Great care has to be taken in handling the ore. o'97 cubic feet
weigh 1 ton. As it is worth £100 per ton upwards, it can be easily-
imagined what great loss would accrue from careless handling. Cast-
iron floors would undoubtedly be the least wasteful but for the great
initial expense. Concrete covered with cement wa*s tried, and did well
where there was no wheel traflic ; the barrows, however, broke it up in
six months. The best floor tried was made of wooden blocks boiled in
tar and arsenic, and laid as close as possible, without other joint than
that formed by the excess of tar.
Preparation of Impure Ores. — The production of good marketable
tin depends greatly on the quality of the ore smelted. It is true that a
great deal can be done to improve bad metal by subsequent refining, but
the results are never really satisfactory. The true way to avoid pro-
ducing tin of inferior quality is to strike at the root of the evil, and
eliminate all injurious impurities from the ore before the furnace i&
charged. The smelter should throw as much of this duty as possible
on the miner. At Pulo Brani a sliding scale is used, by means of which
the price paid for the ore depends not only on the metallic tin it con-
tains, but also on the nature of the impurities present. The chief of
these are mispickel, copper pyrites, and iron pyrites. Wolfram, though
never entirely absent, is not present in sufficient quantities to render
profitable its extraction as tungstate of soda by the Ox land process.
Its chief effect, as also that of the various siliceous and tinaniferous
impurities, is to cause loss of tin by increasing the richness of the slags*
An incredibly small quantity of arsenic, sulphur, or copper in the ore, i&
sufficient to render the tin produced from it useless for all purposes
except that of manufacturing inferior solder. At Pulo Brani any ore
containing arsenic or sulphur is thoroughly roasted at least once. The
furnace is of the "blind roaster" type, the ore being in a muffle out of
direct contact with the fire. The flame from the fire-box passes first
between two arches over the bed and then under it to the flue. During
the roasting the ore is rabbled through the charging-doors along the
side of the chamber, a suitable flue taking away the gases and fumes
evolved. It is found practicable and cheap to roast, when necessary,,
in an ordinary smeltiug-furnace, logs of mangrove wood being used as
fuel, and plenty of air being allowed to pass through the doors of the
fireplace.
When roasted, the ore, unless of very poor quality, in which case it
is treated with tailings, is sluiced by Chinese coolies, and gives " good
headings," which can be smelted directly ; " coarse tailings," which
need to be crushed ; and " fine tailings," which are caught in boxes at
the tail of the sluice?. The " coarse tailings," after being stamped in a
REVERBERATORY FURNACE EMPLOYED AT PULO BRANI, SINGAPORE.
z
o
tij
-J
Id
O
O
z
Q
REVERBERATOEY FURNACE EMPLOYED AT PULO BRANI, SINGAPORE.
TIK SMELTING, 277
•6-head Californian stamp-battery, are again sluiced. The headings
therefrom are re-roasted, and treated on a set of six Frue vanners ;
while the tailings, together with the fine tailings from the first sluicing,
are treated separately, being first somewhat concentrated by passing
through a set of fixed buddies, then again roasted and passed over the
Frue vanners. Some eight sluices are constantly worked. The stamps
are also looked after by Chinese coolies, whilst the buddies and Frue
vanners are tended by Kling or Madras coast coolies.
Although this is the general procedure, it is varied greatly according
to the nature of the ore. Ore containing copper is allowed to stand for
a considerable time between the roastings, to weather as much as
possible and to allow the copper sulphate to drain off. Both machine
and hand-jigs were largely employed at one time, but the latter proved
too expensive to be continued, though they gave excellent results so far
as purifying the ore was concerned.
System of Labour in Mixing Charges. — It is usual in tin-smelting
works for the charges to be mixed by the furnacemen. This ia not a
good plan under any circumstances, and it is impracticable where the
furnaces are worked by Asiatic coolies. At Pulo Brani all work thai
can possibly be so arranged is paid by piece. The coolies work
under the direction of a contractor, subject to a Chinese clerk to whom
the manager delivers his orders in writing, and who is responsible for
the weighing and mixing.
The manipulation of the ore is divided into three sections — (1) Dis-
charging from a steamer at the wharf or from a lighter in the dock,
weighing, storing, emptying into bins or placing the bags at the roaster,
or in the concentrating-shed. This is the work of one gancr paid at
schedule prices. (2) Mixing ; this is the work of a second gang, who
have to take the ore and other materials, weigh and mix them, and
place the charge in a bin in the charging-room, ticketed to show its
destination, at a fixed price per ton. (3) The third stage is the work
of a distinct set of coolies, who wheel the charges from the charge-bins
to the furnace-door, and leave them ready for the furnacemen to put in.
Metal from the furnace to the lighter is treated similarly.
An outline of the detail work of charge-mixing is as follows : — The
bins each contain ore of a certain assay value ; the day^s orders contain
directions for mixing the charges by taking so much ore from each bin,
in order to keep the assay of a charge constant at a given figure. Welsh
anthracite is used as a reducing agent ; and drosses, sweepings, skim-
mings, &c., have to be mixed in ore charges in such ratio as to keep
them down in quantity and prevent accumulations.
The Smelting Furnaces, — The furnaces, as shown, at Pulo
Brani are of the ordinary reverberatory type. There have been many
alterations in them, however, from the pattern originally erected in 1887.
The distinguishing feature of the latest furnace is the water vault. Tin
at high temperature becomes very fluid ; and this property, together
with its comparatively high specific gravity, renders it a most difficult
matter to prevent leakage. Af rer many trials and attempts to entirely
prevent leakage through the bed, all of which failed, it was decided to
278 TIN DEPOSITS OP THE WORLD.
regulate the leaks rather than to try to prevent tbem. The evil of these
leaks is not absolute loss of metal, but trouble and difficulty in recover-
ing it. Tin melts at 260° C. The foundations of a furnace, and the
ground around it, are at or above this temperature for a distance of some
feet. Consequently, any tin that leaks into the vault of an ordinary
furnace below the bed remains liquid, and will slowly but continuously
find its way through the cracks of the ground until it reaches a place
where the temperature is less than 260° C. The distance tin will
travel is incredible to those who have not seen it. The cost of the
periodical recovery of all this metal is very great ; for the metal is-
either in huge lumps of 10 tons or more, or else in fine strings and
sheets into which it has been moulded by cracks in the clay. Sand is
said to form an effectual bar to the passage of melted tin. The ex-
perience showed that at comparatively low temperatures it does act as a
check ; but at higher temperatures the tin and sand become mixed so
completely that separation by heat is very wasteful owing to the oxida-
tion of the metal. Further, anything siliceous round a tin-furnace
should be avoided as far as possible. It will have to be swept up and
treated in a furnace sooner or later to extr^ict the tin ; and the more
silica it contains, the greater will be the quantity of slag produced, and
consequently the greater the loss of tin.
This loss of tin by leakage, with attendant difficulties in recovery,,
have been entirely overcome by the introduction of the water- vault,,
below the bed, containing a depth of 8 feet of water. Any drops of tin
are granulated in this water, and their further passage is effectually
checked. Once a week the water is pumped oiit, and the granulated
metal is recovered. In every case, such explosions as have occurred have
been due to deficiency of water. If care be taken to rabble down any
heaps of granulated metal which form below the water, and if the water-
level be maintained, no explosion of a serious nature can occur.
The bed and lining are the most important parts of the furnace, and
the most difficult to keep in order. It is necessary to build the furnace
in such a way that the bed, lining, and roof can each be repaired or
replaced without disturbing the other parts. The bed is of firebricks
laid on end. In order to reduce the joints as much as possible, the faces
of the bricks are ground true before being laid. They are laid dry, and
forced tight with screw-jacks. The rails which carry the bed lie across-
the furnace, and are divided in the centre. Here they are carried by a
strong iron rail, while their other ends rest on the inner 4J inches of the
wall of the furnace. The large rail is carried at each end of the bed on
smaller rails built into the brickwork, or by pillars built up from the
floor of the vault. Both methods possess advantages. The large rail
is divided in the middle, and is there carried by a pillar. The bed is
laid with a fall of 3 J inches to the tap-hole from eVery part of the
furnace. This fall is secured by placing the rails accurately in position,
the bricks following them. The large rail is first placed accurately
along the centre-line of the furnace, with a fall of If inches from the
front door and bridge. The 4J-inch work which carries the small rail
round the chargiug-door side is levelled ; while that round the tap-hole
TIN SMELTING* 279
side is finished with a fall of 3 J inches from the bridge and front door
to the tap-hole. The cross rails can then be placed in position and the
bricks laid. Sometimes the large rail, instead of being divided at the
middle, is merely beated and bent. This is very troublesome and has
no advantages over the method of dividing the rail. When a bed is
worn out, it can be quickly removed by knocking down the centre
pillar, when the whole collapses. The courses of bricks in the bed are .
laid across the furnace, beginning at the bridge. One course is laid at
a time, and is carefully keyed up while the screw-jack is on. The
bricks are all gauged for each course, ^^ inch excess or defect on the
width (4J inches) being rejected. When the bed is compile it is
grouted with fire-clay cream, dried carefully and heated. The first
charge is cast iron, which, when melted, forms an excellent grout, and
binds everything firmly together.
The lining rises from the red brickwork behind the bed. The end
brick of each course of the bed abuts on the lining, which must there-
fore have a true face and the smallest possible joints. The lining is all
in headers. Where it meets the roof it is finished off by a course of
three-corner end-splayed bricks. The roof, instead of springing from
the lining, springs from the outside work of red brick. As this is only
1 J brick thick, the thrust of the roof is taken by T-iron, built in and
supported by the vertical girders which bind the furnace. The thrust
of the bed of the furnace is taken in the same way by T-iron built into
the brickwork. The bridge is built with as much care as the bed. It
cannot, however, be kept tight, and is therefore built with a cavity^
which is continuous through the outside work. In this way any slag
which leaks through and sets can be knocked ofl:' with a steel bar. Tin
which leaks through the bridge falls into the water in the vault. The
doors of the fireplace are in the back wall opposite to the bridge and
high up. The fireplace is easily filled through these doors, and the fire-
rabble is rarely needed. The coal lies at its proper angle of repose from
the roof above the fire-doors down to the bridge, and there are no empty
corners possible. Winding is done through a cast-iron winding-plate
placed below the fire-doors. The lower row of holes in the plate is
about 9 inches above the bars. This form of fire is very easily worked.
The " flote," or pot into which the metal runs when the furnace is
tapped, is a wrought-iron or steel tank lined on the bottom with 9-inch,
and round the sides with 4J-inch firebrick. These leak in spite of all
efforts to keep them tight, and the water-vault has been extended under
them with good results. In case of any hot material getting through
the bed with a rush, two pipes, 1 8 inches in diameter, are built into the
thick corner of the furnace in order that the steam may escape freely.
The working of the furnace is as follows : Suppose a charge has
just been drawn. The doors are open and the bed and walls are
inspected. If much worn and eaten away they are " fettled." A mix-
ture of bauxite and fireclay moistened with water is put on the worn
place with a paddle, and is rammed home with the head of a rabble.
When all the bad places are covered, the doors are lowered and the
fettling is " glazed " by hard firing for about an hour. This fettling
280 TIN DEPOSITS OF THE WORLD.
should be required only once a week, in addition to that given when the
furnace is overhauled on Sundays. When the furnace is hot and ready,
the doors are opened, the damper is closed, and the charge is thrown on
the bed through the side doors, while the leading coolie levels it with a
rabble through the front door. The charge being all in, the doors are
closed and the fire is made up as large as possible. Meanwhile the
charge- wheelers bring out the next charge and tip it under the charging-
doors, and one of the four furnace coolies turns it into two heaps, one
under each door. The leading coolie then turns his attention to the
slag-beds, and prepares them to receive the slag from the charge. As
soon as he sees that a fresh fire is needed, he calls the European smelter,
who, after inspection through the peep-hole in the front door, decides
whether to put on another fire or to rabble the charge. With good coal
the first fire should last two hours or longer. This gives the charge a
proper start, after which it may be rabbled. It should be liquid near
the bridge, and only moderately thick at the tap-hole, where it is
deepest, and towards the front door, and frothing freely all over. A
good rabbling at this stage should free it from the bed, and mix it
thoroughly. The fire is again made up as full as possible, and when it
has burned clear the rabble is again used to ensure that everything is
loose from the bed. At this time the surface of the charge in the
furnace should be resplendent and free from floating lumps and patches.
If so, the door is closed, another fire is put on, and the tapping-bar is
withdrawn. A stream of tin f inch in diameter escapes and falls into
the flote. At this rate it requires about forty minutes for all the tin to
drain out, leaving only liquid slag in the furnace. When it has been
ascertained that all the tin is out, the tapping-bar is again inseHed, and
the channel from the tap-hole is altered to deliver over the slag-beds.
The whole of the clay stopping of the tap-hole is removed, and the slag,
rushing out, fills the slag-beds. The tap-hole is then closed, and the
furnace is recharged.
Metallurgical Processes, — The metallurgical processes employed
may be conveniently considered in four parts.
(A) Smelting ore, with the production of " rich *' slag and " ore
metal " ; (B) Smelting rich slag, with the production of " poor " slag
and "rough metal"; (C) Treatment of poor slag containing tin as
prill ; and (D) Refining the metallic products of (A), (B), and (C).
(A) A charge is made up by mixing ore with between 13 per cent,
and 15 per cent, of culm or anthracite, and about 3 per cent, of refinery
dross. If the quantity smelted at one time is 4 tons, the composition of
the charge would be somewhat as under : —
Ore
Culm
Dross
Poor Ores,
65 per Cent,
and upwards.
Rich Ores,
71 per Cent,
and over.
Owt.
80-0
10-4
24
Cwt.
800 1
12-0 1
2-4 i
TIN SMELTING. 281
The time required for a charge should be seven hours or eight hours
with good coal and labour, but sometimes longer periods are required.
From a charge of such composition there should be obtained 45 cwt. to
48 cwt. of metal containing about 99*5 per cent, of tin, and 29 cwt. to
30 cwt. of rich slag containing 30 per cent, to 40 per cent, of tin.
The metal from these charges is hard, brittle, and dull in colour ; it
is rather greyer than refined tin, and if poured hot, it may be covered
with beautiful iridescent films of oxide.
The slags produced at this stage, distinguished as " rich slags," are
variable in appearance — sometimes dark brown and highly crystalline,
and sometimes quite black and glassy. In thin sections they show
under the microscope a yellow matrix with numerous black crystallites.
Reflected light shows tin prills, and at times a brown substance, probably
ore that has only been fused. Their composition varies widely. Speci-
mens examined contained 35 per cent, of tin, 15 per cent, of silicon,
18 per cent, of aluminium, and 9 per cent, of iron, in addition to man-
ganese, titanium, lime, and magnesia.
(B) There are many ways of smelting rich slag. They may be
tabulated as follows ; — (1) smelting rich slag with excess of scrap-iron
and culm to produce " hardhead " and poor slag unfit for further use.
This method alone is not desirable, as the hardhead produced (an alloy
of iron and tin very difficult to separate) is difficult to treat further.
(2) Smelting rich slag with culm and sufficient iron to decompose the
tin silicate. The difficulty with this method is the danger that the slag
produced should be too rich to throw away ; but the metal (termed
DiAGBAM SHOWING THB PROCESSES OF SMELTING.
Ore smelted with
anthracite and
— ^refinery dros«.
Rich slag, smelted Ore-Metal,
with anthracite, liquidated,
iron and rough &c.
-metal dross.
Poor slag, Rough
treated to metal,
recover prill. liquated.
: ,T ^ Prill, I , I
tPoor slag, liquated. I >^ ,
cleaned. [ |
Refuse I Slag metal, ,
I slag. I liquated,
' ^— I Rough &c.
~ ] metal dross. ' I — >
I Refinery Market
I dross. Tin.
282 TIN DEPOSITS OP THE WORLD.
" rough metal ") is fairly soft and not diflScult to refine. (3) A com-
bination of the first two methods, by which hardhead is first produced
by excess of iron, and is subsequently smelted with more rich slag ; the
result being that the rough metal is fairly easy to refine, and the slags
are sufficiently poor to be rejected. The process, however, requires
great care, both in mixing and smelting.
In refining the metal from slag, whatever process is employed, a
heavy black dross always remains, containing iron oxide and tin oxide.
This is called "rough metal dross," and has to be worked up con-
tinuously. The two following methods of working slag are therefore
also used : — (4) Rich slag is smelted with culm and rough metal dross,
producing rough metal and poor slag — a process which also requires
great care— or (5) Rough metal dross is used to replace hardhead in
process (B) (3). The greatest objection to all these and similar pro-
cesses is their intermittent nature. Continuous and regular work is
most desirable in metallurgical as well as in other industrial processes.
The mixings required for the above processes are respectively as
follows : — (1) 1 J ton of rich slag per charge mixed with 20 per cent, to
27 per cent, of iron and 23 per cent, to 26 per cent, of culm, according
to the richness of the slag ; (2) IJ ton of rich slag with 16 per cent, to
20 per cent, of iron and 20 per cent, to 25 per cent, of culm, according
to the richness of the slag ; (3) 1 J ton of rich slag with 62 per cent, to
70 per cent, of hardhead and 24 per cent, to 25 per cent, of culm ;
(4) IJ ton. of slag with 62 per cent, to 70 per cent, of rough metal
dross and 20 per cent, to 24 per cent, of culm. A 1 J-ton charge should
be smelted in a furnace similar to that described for smelting ore.
In all the foregoing methods of extracting tin from slag, iron is
used, and there is difficulty in ensuring that the exact quantity may be
used so that pure tin and pure iron silicate may be obtained. The
result always is, that to get a silicate of iron approximately free from
tin, excess of iron has to be used, which alloys with the tin, giving rise,
when the tin is refined, to rough metal dross. Therefore some of the
iron added to the rich slag is lost as silicate, and some returns as rough
metal dross. If, then, the ratio of these two quantities be found, the
slag may be smelted with rough metal dross and iron in such quantity
that the amount of rough metal dross obtained from a charge and added
to the charge is equal and constant, while the iron added is just equal
to that thrown away as silicate.
The quantities are thus found to be : — Slag, 30 cwt. ; dross, 6*5 cwt. ;
iron, 2*75 cwt. ; but the slag resulting from this rational composition of
the charge was too rich. An addition of rough metal dross led to the
disappearance of this trouble, and the proportions adopted were : —
Slag, 30 cwt. ; dross, 12 cwt. ; iron, 2*75 cwt. The excess of rough
metal dross can do no harm, as it only circulates unchanged. In addi-
tion to these constituents culm has to be added. Slag is ferrous silicate,
and a reducing action must take place simultaneously with the replacing
action. Coral or lime in any form is also added as a flux to combine
with some of the silica present. It is easy to add too much, in which
case it combines with the oxide of tin present, and carries it into the slag.
TIN SMELTING. 283
The final composition of the charge would be, therefore, slag,
30 cwt. ; dross, 12 cwt. ; iron, 2*75 cwt. ; culm, 6 cwt. ; coral, 2*4 cwt.
This method of smelting slags gave satisfaction in every respect. The
details of the process are similar to those given under ore smelting. In
smelting slag, however, though the furnace and fuel may be the same,
a much higher temperature is attained than when ore is smelted, the
duty of the fire being less. It is safe to assume that, in ore smelting,
the chemical change represented by the equation SnOa + 2C = Sn4- 2C0
takes place to some extent, and this, being an endothermic reaction,
may account for the lower temperature of the ore furnace as compared
with the slag furnace, other things being constant. Whatever may be
the reaction that takes place with slag charges, it is but slightly
endothermic compared with the reaction between the ore and carbon.
A slag charge is rabbled three hours after charging, and again an
hour later, by which time the charge ought to be well off the bed and
the rough metal ready for tapping. The reaction between the slag,
iron and culm takes place with considerable violence. When the froth-
ing and bubbling has ceased, the charge is again rabbled, the rough
metal is run into the flote, and the slag into moulds. A slag charge
should not require longer than between six-and-a-half hours and seven
hours.
The products of melting slag are " second," or " poor," slag, and
rough metal. The poor slag obtained is hard, black and glassy. In
thin sections under the microscope it shows here and there a small
amount of yellow matrix ; but it seems to consist chiefly of a dark
black crystalline body with the crystals closely packed together. It
varies greatly in composition, containing 60 per cent, of silica with
varying amounts of other bodies that are also found in the rich slags.
This slag contains numerous lumps and prills of tin. The lumps are
removed by hand-picking after the pigs of slag fall to pieces. The
finer prills are recovered as described subsequently, (C). The rough
metal is ladled from the flote into moulds and is stirred, while liquid in
the moulds, with an iron rod. This stirring is most important, as other-
wise the ingots would tend to set in two distinct layers, the lower and
larger portion being practically hardhead, an alloy having a high
melting-point, while the upper layer would be nearly all tin, holding a
little iron in solution. The same result is attained by granulating the
metal. In both methods the metal is constrained to set as a uniform
alloy, or mixture of two alloys, and is much more capable of economical
liquation in the subsequent refining. The metal is black and dirty in
appearance ; it is very brittle, and the fracture is steel-grey.
(C) The recovery of the prill may be effected in two ways ; (1) by
crushing and washing it, as is the practice in Cornwall and Tasmania,
and (2) by " running " it in a furnace. The first method was tried at
Pulo Brani, but was abandoned, owing to the large amount of the metal
reduced to slimes, and rendered difficult of recovery. Slag metal, as
pointed out above, is very brittle, and hence it easily forms slimes. The
second method is more effective and not more expensive. It consists
of re-melting the slags and allowing the metal to sink to the bottom of
284 TIN DEPOSITS OF THE WORLD*
the liquid charge. It is not necessary to treat all the second slag in
this way. By making the first two moulds in the slag-bed deeper than
the others, practically all the metal which does not run into the flote
can be collected in these moulds ; and the slag in the remaining moulds
(more than two-thirds of the total quantity) can be thrown away as
clean. This leaves less than one-third of the slag to be treated. In
this process no chemical change has to be effected ; a given mass has
merely to be melted and then run off ; consequently, the amount of fuel
required is not large.
The charge is rabbled two hours, and again three hours, after charg-
ing, after which the slag only is run off. About three times in the
week, the metal which has collected on the bed is tapped off, by giving
the furnace another fire after the slag has been tapped ; the metal pro-
duced being run into sand moulds, and broken up to convenient-sized
lumps while still red-hot. This is necessary on account of the extreme
toughness of the hardhead when cold ; when it is hot there is no trouble
in breaking it up. The metal can, however, be treated in the same way
as other rough metal, and stirred in the moulds or run into water. A
charge would contain, slag, 40cwt.; culm, 2*5 cwt.; and coral, 2*5 cwt.
If the slag is free from combined tin, the coral and culm may be
omitted. They are only added to effect a further reduction of any
combined tin in the slag. Four hours is a full allowance for treating
these charges.
(D) Liquation is the method principally adopted for refining at Pulo
Brani ; but " boiling " is sometimes resorted to under special circum-
stances. The ingots, or granulated metal, are piled in a furnace heated
to incipient redness, wood being used as fuel. Metal which has not
been stirred in the moulds, or which has not been granulated, when thus
treated, would leave behind large lumps of hardhead in place of the
powdery rough metal dross. The products obtained from liquating
rough metal, if properly conducted, are about 90 per cent, of " slag-
metal," containing 99*5 per cent, of tin; and I'd per cent, of rough
metal dross, containing about 65 per cent, of tin, and 25*5 per cent, of
iron, partly as oxides and partly as alloys. This dross is mixed into
the slag charges, as has been shown, and circulates in constant quantity.
The metal from this liquation is of about the same composition as
*^ ore metal," and its further treatment depends on its destination. For
ordinary commercial tin, suitable for making tin plates, solder, or for
use in galvanizing, it would be mixed with ore metal, and the two
finally refined together. Tin required for making foil or for chemical
salts must be very pure and free from iron. It is best in making this
quality to avoid any mixture of slag metal, but, if this cannot be
avoided, the slag metal must be boiled before it is mixed with ore
metal, or the mixture must be boiled after the second liquation.
Boiling is usually performed only on such ore and slag metal as has
been derived from ores that have needed roasting and dressing. It
consists merely in immersing logs of green wood in the molten metal.
The tin is kept just above its solidifying point by a sm«ll fire under the
kettle. The operation lasts for several hours, until the bubbles of
TIN SMELTING. 285
steam from the wood cease to bring scum to the surface of the tin*
The wood is then lifted out, and the metal is skimmed, ladled into
moulds, and sent to the refinery, the skimmings being added to the slag
charges.
The slag metal is then fit to enter the refinery. The operations
performed in it are liquation, followed by " tossing," which consists in
allowing molten tin to fall from a height into a mass of liquid metal,
thereby carrying air into the mass and permitting a certain amount of
oxidation. The liquating furnace is a rectangular chamber with a fire
at each end ; the smoke leaves by a chimney in the centre of the arch*
The ingots are piled on the bed and wood fuel is used. The tin runs
continually through the open tap-holes of the refining-furnace into the
two kettles which are situated in the pouring-room. In these the metal
is allowed to stand for twenty -four hours, after which it is skimmed '
and poured into moulds. When cool, the ingots are weighed, and are
then stored ready for sale in the ingot room, whence they can be readily
loaded into boats at the small wharf. The tin is kept liquid in the
kettles at a temperature of as nearly as possible 260° C. On standing,
nearly all the remaining impurities settle out from the tin to the bottom
of the kettles, and for this reason the bottom 12 inches or so of metal
remaining in the kettles is sent back to the refinery to be liquated
again.
After liquation in the refinery furnace, the ingots of metal leave
behind on the bed of the furnace a grey, powdery body. This sub-
stance is known as " refinery dross," and is taken to the mixing-room,,
where it is added to ore charges. One hundred parts of ore metal will
give about 96*o parts of fine metal and 4*5 parts to 5 parts of dross.
Refinery dross is a mixture of the oxides of tin and iron with less easily
fusible alloys of the two metals. It contains about 65 per cent, of tin
and 11*5 per cent, of iron.
Marketable Tin, — Ingots of good tin should on cooling have a clear,
bright surface, with a slight depression on the top, and the crystalline
appearance of the surface should show a large pattern. The metal
should be soft enough to be marked by the finger-nail, should bend
easily, and, if partly cut and then bent, the strained surface should have
a smooth, silky lustre, appearing rather as if it had been pulled out than
either torn or broken. Impure tin will give the " cry " of tin on bending;
but, on cutting and bending the brittleness of the fracture will increase
with the impurity. The latter is the only test used by the buyers in
the Straits Settlements. It is unsatisfactory, as the four corners of an
ingot can be cut and bent so as to show four distinct qualities. The
best test is to roll out a piece of the metal. Inferior tin will then show
cracks along the rolled edges, and, if the rolling is fine enough, pin-holes
will appear through the foil.
Loss of Tin, — One hundred parts of ore, containing 70 parts of tin,
oQ parts of ore metal are obtained in (A), which is sent to the refinery,
and some 36 parts of slag, containing 12 parts to 13 parts of the
original 70 parts of tin. As the dross from the refinery is sent back to
the ore furnace, it may be considered that in the end the whole 56 parts.
286 TIN DEPOSITS OF THE WORLD.
will be obtained. In (B) and (C) the loss of tin commences, and
(iepends upon the amount of poor slag produced, and its richness in tin.
The latter may be taken on the average at 5 per cent., and, as 36 parts
of rich slag produce about 27 parts of poor slag, the amount of tin
thrown away as poor slag will be 1*35 parts, or nearly 2 per cent, of
the tin started with. The loss by splashing and theft will bring it up
to somewhat over 2 per cent, of the total amount of tin brought into the
works. Considering the various "refining processes (D), it is clear that
when once the work is continuous no loss of tin would take place there;
for the various drosses, as in the case of the refinery dross, are returned
to the smelting-furnaces. This applies also in the case of the prill in
the poor slag, which is returned from (C) to (B).
Consumption of Iron, — It will be evident that the iron added to
the slag charges, viz., 2*75 parts in 30 of slag, or 9*17 per cent., is
thrown away in the poor slag. Rich slag is about 36 per cent, of the
ore, or 50 per cent, of the tin contained in the ore ; therefore the con-
sumption of iron is 4*7 per cent, of the tin obtained.
Consumption of Culm, — This amounts to about 17 per cent, of the
ore smelted. If the action of reducing tin ore were exactly represented
by the equation SnOj + 2C = 2CO + Sn, the culm required would be
18 per cent. Anthracite landed in Singapore is expensive, and experi-
ence has shown fhat coal of good quality may be used to replace it.
It is necessary, however, to use about 10 per cent, more of the latter.
Charcoal may be used, but it is very destructive to the furnace,
especially to the flue and " verb," or entrance to the flue from the
furnace. This is probably due to the potash and soda it contains.
Consumption of Fuel, — The coal used at first was chiefly Australian.
Latterly this has been almost entirely replaced by Japanese coal, and
still more lately, owing to the rise in price of the latter coal during the
war, it has been replaced by coal from Labuan and the Tonkin coal-
fields. As the wharves at the works allow ships of 3,000 tons to come
alongside, the price of freight is not so high as might be expected, and,
except during the wool and wheat seasons, freights are low. The
varying cost of coal necessitated a large storage capacity at the works.
The coal-sheds are capable of holding about 12,000 tons, and even this
quantity proved insufficient on one occasion. The consumption esti-
mated on the average of many months' regular work, for all purposes
(including boilers, blacksmith, etc.), in smelting ore averaging 68 per
cent, net return, is 1*15 ton of coal to 1 ton of ore.
Tin Smelting at Banca.*
Although the need has long been felt for subjecting to chemical
checking the metallurgical processes which take place iu the smelting
of tin at Banca, this has hitherto not been carried out owing to the
* Specially translated for " The Mining Journal " from the " Jaarbeck van het
Mijnwezen," by J. Kooman?.
TIN SMELTING. 287
lack of the necessary equipment. In the 1872 Year Book of Mining,
Part I., there are indeed some figures stated which relate to the quantity
of tin obtained from smelting ore and slag, but particulars are wanting
regarding the assay of the smelted ore.
In 1905 a quantity in round figures of 14,000 kilogrammes of ore
was smelted under chemical control, the object being to ascertain the
quantity of tin obtained, the amount lost, and what became of this lost
tin. Where the quantities of slags and tailings obtained were sufficient
to admit of the ordinary process of dressing, they were further treated
Before all the chemical analyses had been completed the investigation
had to be interrupted owing to departure from Banca. The figures
already obtained, however, furnish a good view of the operation of the
processes, as may appear from the following.
To contribute to a clear comprehension of the figures which will be
given, it must first briefly be stated what processes of treatment tin,
ore, slag, and intermediate and waste products undergo at Banca. This
will complete but not repeat the description already given in the Year
Book, which may be consulted.
Short description of Smelting at Banca.
The first smelting still takes place in the "Flanders " furnace, a
"gutter furnace with open twyer," described in the Year Book of 1872,
Part I.; the furnace has only undergone some slight modifications. Its
dimensions are somewhat larger. Formerly 35 to 40 pikuls of tin per
night shift were obtained, whilst at present 55 to 60 pikuls of tin can
be smelted per night. Further, the ratio between height and section
has been somewhat modified in the course of time, the furnaces having
grown somewhat broader.
In addition, in 1889 a second vessel was placed next to that beneath
the outflow opening of the furnace. In the first vessel the tin has the
opportunity to settle, and the pure tin flows over into the second. This
tin is of such great purity that it supplies commercial tin direct in the
well-known block form.
While previously, in order to obtain the well-known tin blocks the
moulds were straightway filled to the edge, this method of casting was
abandoned three years ago, as it was found that blow holes formed in
each block of tin, which during transport were filled with water,
making its way through microscopical crevices. By casting in four
layers, the following layer being only cast just when the previous one
shows signs of solidifying, and by using extremely hot tin for the
topmost layer, blocks are obtained showing no blow holes, or very
insignificant ones.
The impure tin (impure chiefly owing to the presence of iron) which
settles in the first vessel is cast into blocks when the night smelting is
over, to be subjected later to refining. This tin, called residual tin,
forms about 7 per cent, of the entire output.
288 TIN DEPOSITS OF THE WORLD.
The manner in which the tin slag is prepared for slag is described
in the technical section of the 1883 Year Book. When the fluidity of
the slag is insufficient, it is sought to make an improvement by adding
lime. The tin obtained by melting the slag from the ore smelting i&
further refined owing to poorer quality.*
During the last two years the slags which were rejected as worthless
by the mining " kongsies ''t or the slag smelters (under the system of
payment in force), have once more been taken in hand for treatment ;
but this is now done by the Government direct ; that is to say, the
work is carried out on a daily wage system.
These slags are crushed fine and classified according to size of grain ;
each sifting product is washed separately, and the heavier material
thus separated is smelted in a small round shaft furnace with open
twyer 0*9 metres in height, and having not more than 0*3 metres
internal diameter. To render the furnace easily accessible for cleaning
the shaft rests loose on the floor. A hand blast supplies the necessary
air.
Refining.
The refining of the residual and slag tin is carried out in a liquation
furnace consisting of a series of six cast-iron plates arranged above each
other in the manner of roofing tiles, and heated from below. The
plates are at slight inclinations of 5 to 9 degs., the lowest being most
horizontal, and each higher one at a greater slope.
The refining tin is usually yielded on the second and third plate
only, the pure tin flowing off and the impurities remaining behind.
The dross left behind is transferred to the fourth plate by means of a
shovel. Owing to the removal of the tin by liquation, the remaining
mass becomes continually harder ; in order to get any more tin to flow
out the temperature must be slightly raised. The hearth is therefore
arranged in such a way that the plates lying higher up are heated more
than the lower. The mass of dross on the fourth plate, when it yields
no further appreciable amount of tin, is shifted to the fifth and then to
the sixth plate. On these two plates it is only by pressing that any tin
can be made to flow out. This exudation is effected by compressing
the tin against the raised ribs provided on the edges of the liquation
plates. The tin flowing from the liquation plates is, in order to
give the accompanying impurities of higher specific gravity than the
pure tin an opportunity to settle, conducted into a settling tank, and
from this successively into two cast-iron pans placed stepwise beneath
each other ; it always flows over into the following tank. From the
last pan the tin is cast in blocks.
The temperature of the settling pan may not be higher than is
* All tin obtained from poor ore such as gangue ore (" gangert8")i ore obtained
by re-washlDg already used-up soil, alluvial tin ore containing pyrites, etc., are
likewise refined.
f Piecework contractors.
TIN SMELTING. 289
necessary to maintain the tin in liquid condition. It can be regulated
by allowing a cold current of air to flow in contact with the bottom.
The impure tin which then settles at the bottom possesses a higher
smelting temperature than pure tin ; this property renders it possible to
remove the impurities by means of a perforated ladle, and to purify the
tin bath in this way. The impure tin thus removed is once more
transferred back to the liquation furnace.
The pan between the settling tank and the casting pan serves for
cheeking purposes only ; from time to time small assay bars are cast in
order to examine whether the tin still fulfils all requirements as regards
purity.
It occasionally happens that the tin contains impurities which can
only be separated by poling, as, for instance, occurred in 1898 in
Muntok. Fresh wood is then plunged into the tin bath, and, owing to
the gases which develop, a scum forms, which consists for the most
part of tin, but in addition embodies the impurities. The scum can
easily be taken off with a perforated ladle.
The tailings or waste from the liquation furnace, partly granular
and partly pulverulent, are in some measure converted into oxides
owing to the high temperature of the plates. They still possess a high
tin assay, and are therefore melted in the Flanders furnace. Part of
the impurities scorifies, but the greater part is retained in the outflowing
tin. This impure tin is once more refined, but a second liquation is
necessary in order to obtain entirely pure tin from it.
On the average one liquation furnace with two shifts of eleven men
yields 500 blocks weighing 285 pikuls (17 tons) of refined tin every
twenty-four hours. Of each shift three men are occupied with the
liquation, one man is engaged in stoking, two men in casting, and five
men on various work. The consumption of wood fuel (the furnace is
heated by wood) amounts to 0*020 cubic metres per pikul of tin refined.
The wood used is bakau wood, the price of which in Banca varies
between fl. 2 and fl. 2*75 per cubic metre. The wages paid are fl. 0"15
to fl. 0*20, and sundry expenses, lighting, &c., 3*5 to 5 cents per pikul
of tin refined.
The total cost of tin refining in Banca varies from 25 to 30 cents
per pikul of tin refined.
The drawing appended represents a double liquation furnace ; that
is, two liquation furnaces with a common smoke stack. This is the
form in which it is usually built in Banca. If in earlier days there
was a possibility of isolated blocks of inferior quality being put upon
the market, the measures taken during the past few years, as described
above, have rendered it impossible for blocks containing any considerable
quantity of impurities to be shipped. The average purity of Banca tin
has therefore advanced.
Between the tin originating from the first smelting process and
refined tin no distinction is made, because a number of chemical
analyses have shown that no difference in quality can be found ; both
kinds are of great purity.
290 TIN DEPOSITS OF THE WORLD.
Results of the Examination,
The assay was always carried out with ore from mine No. 2
Blinjoe, which mine is worked in the upper reaches of the Soengei
Boeboes. The ore had a size of grain of 0*2 to 4 millimetres.
Kilogrammes.
Air-dried ore weighed off 14,579
(The contents of moisture amounted to 0*15 per cent.)
If deduction be made for this amount of moisture, the
weight of the tin ore is found to be - - - 14,557
With this ore three tin assays were arranged ; for
each assay a fresh sample was taken on the diagonal
method. The average found was 72*97 per cent.
of tin. The tin, therefore, contained in the ore is 10,622
The tin value of the valley ore on Banca reached a somewhat
higher average.*
The smelting of this mass of ore required three smelting nights.
During the first and second nights an approximately equal quantity of
ore was smelted, but during the third night about one-sixth less.
As is customary in smelting ores, the slags were once more smelted
towards the end of the night.
1st Night. — Began smelting at five o'clock p.m., terminated on the
following morning at nine o'clock. Duration of smelting thus sixteen
hours. Obtained : —
Kilogrammes.
87 blocks of shipping tin, weighing - - 3,135*5
and 9 „ of residual tin, weighing - - - 321*2
Total - - 3,456*7
Consumption of charcoal, 208 baskets, one basket containing on
the average 24 kilogrammes of charcoal ; in all, therefore, 4,992
kilogrammes.
The number of blocks of residual tin were somewhat larger than
necessary ; the furnace was new, and the first receiving vessel made
somewhat too large. By lowering somewhat the outflow opening into
the second vessel, the desired number of blocks of residual tin was
obtained on the second and third nights.
2nd Night. — The smelting was begun at 3.30 p.m. and ended at
7 a.m. ; time, therefore, 15i hours. Obtained : —
Kilogrammes.
93 blocks of shipping tin, weighing - - 3,361*3
and 7 „ of residual tin, weighing - - 251*6
Total - - 3,612*6
* See " Year-Book of MiniDg," 1897, page 182.
TIN SMELTING. 291
The charcoal consumed was likewise 208 baskets, or 4,992 kilo-
grammes.
3rd Night. — The smelting began at 3 p.m. and completed at
7.30 a.m., thus covering 16^ hours. Obtained : —
Kilogrammes.
78 blocks of shipping tin, weighing - - 2,802*8
and o „ of residual tin, weighing - - - 180*1
Total - - 2,982-9
The charcoal consumption was 188 baskets of an average of
24 kilogrammes = 4,512 kilogrammes. Hence the total obtained
dm'ing the three smelting nights was : —
258 blocks of tin for shipment, weighing - 9,299*6
and 21 „ of residual tin, weighing - - 743'9
In all 279 blocks, weighing 10,043*5
forming 68*99 per cent, of the dry ore.
From the tin for shipment an average sample was taken by running
off a proof bar before and after every cast of ten blocks, and afterwards
sawing these test bars through. The chemical composition of the
shipping tin appeared to be : —
Tin 99*87 per cent.
Iron 0*13 „
There were not even traces* to be found of lead, copper, or silver.
This tin does not represent the average of Banca tin ; in conjunc-
tion with the somewhat inferior quality of the ore smelted, the contents
of tin are slightly lower than usual. It may, nevertheless, be described
as very pure.
The residual tin had the following average composition : —
Tin - - - - - - 98*82 per cent.
Iron 1*05 „
Sulphur - - - •• 0*11 „
Copper 0*01 „
Lead 0*01 „
In order to determine the average composition, the twenty-one
blocks of residual tin were sawn through the centre and a sample taken
from the saw filings.
These three smelting nights yielded a total of 2,020 kilogrammes of
slag, weighed directly after smelting was completed, and, therefore,
still moist with the water with which they had been quenched. This
extinguishing of the red-hot slags is for the purpose of making them
easy to crush later. After they had been dried they were crushed fine
in a Carr's disintegrator and sifted. After these operations they only
weighed 1,740 kilogrammes. This loss of weight must be attributed,
in the first place, to the drying ; but also in part to the escape, as dust
T 2
292 TIN DEPOSITS OF THE WORLD.
of charcoal which the slag contained and which was crushed to fine
powder by the disintegrator.
The slags were, by sifting and hand selection, divided up into three
parts, namely : —
Kilogrammee.
A. — Fine part, width of mesh f mm. - - - 471
B. — Coarse part, width of mesh 4 mm. - - . 1,249
C. — Sifted pieces of tin and large pieces of tin sorted
by hand 20
The tin assay of each of these three lots and, likewise, the charcoal
contents of A and B were determined. These figures, calculated for
the entire quantity of slags, yielded the following amounts : —
14*5 per cent, of charcoal and
26*3 per cent, of tin.
In lot B some pieces of slag were picked out — which showed no
visible tin beads — for closer chemical examination. They were found
to contain —
Tin, partly in metallic form and partly present as
SnO, 16*0 per cent.
CuO . - - - . - - 0-4 „
TiO, 0-7 „
WO3 0-2 „
Whilst in the residual tin a trace of lead was found, the slag appeared
to be free from lead.
The following calculation may serve to ascertain the loss of tin —
due to ore smelting : —
Kilogrammes.
Quantity of tin present in the ore - - - 10,622
Quantity of tin for shipment obtained,
multiplied by the assay — i.e., 9299*6 x
99-87 per cent. 9,287-5
Quantity of residual tin obtained, multi-
plied by the assay— i.e., 743-9 X 98-82
per cent. 735-1
Quantity of tin contained in the slags —
1770 X 26-3 per cent. - - - 465'5
10,488-1
Lost in smelting - - - - 133-9
Expressed in percentages, 1-26 per cent, of the tin present in the
ore was lost, or 0*90 per cent, of the weight of the ore.
This loss must be attributed —
1. To the finer ore being blown away from the furnace and to
evaporation of tin. This could be met by fitting a chamber for catching
the volatile dust.
TIN SMELTING. 293
2. Owing to the smelted tin sinking and being lost in the furnace.
Part of the lost tin is reclaimed when the furnace is demolished and
the floor of the smelting room broken up and washed. The fine ore
blown out of the furnace is — as much of it as settles in proximity —
trodden into the clay floor of the smelting house.
It is impossible, owing to the lack of data, to state in figures what
is the quantity of tin later reclaimed per smelting night.
Treatment of Slag,
Slags before smelting are first washed in a small trough.
This operation removed from lot A 199 kilogrammes, and from
lot B 548 kilogrammes ; in all, therefore, 747 kilogrammes, of which
245 kilogrammes must have been charcoal. Hence, there were sub-
jected to one smelting —
Kilogrammes.
Fine slag up to J mm. size of grain - - - - 272
Coarse slag up to 4 mm. size of grain - - - - 701
Minute fragments of tin - 20
Total - - - 993
The smelting took place in a small furnace, entirely similar to the
" Flanders " furnace, but only of half its capacity. The smelting lasted
from 10 in the morning till 7.30 in the evening ; 46 baskets of char-
coal weighing 1,100 kilogrammes were used. During the smelting the
slags which had once passed through the furnace were once more
crushed, washed, and fed in again. In this way a further 390 kilo-
grammes were washed away.
There were obtained —
Kilogrammes.
Eight blocks of slag tin, weighing - - - - 277*5
Tin residue in the collecting vessel _ - _ o*75
Slag - - 357
This quantity of slag is too small to be further treated alone.
The tin had the following composition : —
Tin 97-83 per cent.
Iron 2-17 „
Copper ------- trace.
Sulphur ------- trace.
To obtain an average sample the blocks were again sawn through.
The 357 kilogrammes of slag were, in order to obtain an average sample
to determine the tin assay, crushed fine in the disintegrator. The tin
assay appeared to be 10*56 per cent., of which 4*1 per cent, could be
sorted or sifted from the slag in the shape of tin beads. The slag tin
contained 278*25 X 97*83 = 272*2 klg. of tin. The slag contained
357 X 10*56 = 37*7 klg. of tin.
294 TIN DEPOSITS OF THE WORLD.
The slags from the ore smeltiug coutained 46o'5 klg. of tin. Thus
there were lost 155"6 kilogrammes, which cau partly be recovered at
the mouth of the trough or sink, and have partly disappeared by
evaporation and by air current in the furnaces and elsewhere. It may
be assumed that from the 357 kilogrammes of slag which remain from
the slag smelting 5 per cent, of tin may still be won by a repetition of
this process, making in all 17"8 klg. The 892 klg. of slag washed
away were, owing to the smallness of the quantity, not further treated
by the method given above.
At Blinjoe a large lot of slag of the same origin as the above had
its tin assay determined. This appeared to be on the average 8*1 per
cent. From this slag one-fifth of the tin contained was got ; that is,
1*6 per cent, of the weight of slag.
It may be assumed that the 892 kilogrammes of slag in question
being of the same quality will, on further treatment, yield a like pro-
portion, i.e., 892 kilogrammes X 1*6 per cent. = 14*3 klg.
The 743-9 klg. of residual tin, the 278*3 klg. of slag tin, and the
17 '8 and 14*3 klg. of slag tin to be extracted by further treatment of
the slag, making in all 1 054*3 klg., must be subjected to refining on the
method described above ; the quantity is, however, too small to be
worth separate treatment in the liquation furnace.
It may be taken as an average that in refining in Banca the first
liquation yields 94 per cent, of the weight of the tin to be refined in
the form of tin ready for shipment, and a further 4 per cent, is yielded
by smelting the waste and fresh liquation of the product thus obtained.
As to the above-named lot of tin, it may be assumed by analogy that
1033*2 klg.^of marketable tin will be yielded.
In 1904, in refining at Djeboes, by casting a test bar before and
after each casting, the average composition of the tin refined during the
year was investigated.
This appeared to be —
99*92 per cent, of tin, and
0*08 per cent. iron.
No trace even of other impurities could be found. The refined tin
is therefore equal in quality to the other marketable tin.
Results.
Apart from the fact that later on, when the smelting house is
demolished, some tin will be obtained, we arrived at the result that
14,557 klg. of tin ore with an assay of 72*97 per cent, will yield, upon
the method of treatment in use in Banca, 9299*6 kilogrammes +
1033*2 kilogrammes = 10332*8 klg., or 70*98 per cent, of marketable
tin with an average assay of 99*88 per cent., and that there will be lost
10622 = (9299*6 X 99*87 per cent. + 1033*2 X 99*92 per cent.) klg.
= 302 klg., or 2*07 per cent, of the weight of the tin ore.
TIN SMELTING. 295
Smelting Costs,
Wages and implements in smelting ore in Banca account for a cost
of 40 to 45 cents, per pikul of tin smelted, including residual tin. The
costs of the charcoal used differs in a great degree. According as the
smelting establishment is closer to or farther from the wood where the
charcoal is burnt, and as the distance of transport of the charcoal
varies, the prices paid' for the charcoal differ, and are contracted for
with the charcoal burners at fl. 1*05 to fl. 2*20 per pikul of smelted
tin.
The costs of crushing and washing the slag, preparing it for smelt-
ing, also vary to a fair extent, owing to difference in quality. It may
be assumed that as a rule not less than fl. 3 and not more than fl. 6 are
expended per pikul of tin smelted. The outlay for the smelting slag
per pikul of tin produced is somewhat higher than in smelting ore,
because a night of work, the costs of which are the same, yields 20 to
25 per cent, less of tin. Payment for the charcoal consumed is similar
to that in ore smelting.
The re-treatment of the slag removed by washing and originating
from the first treatment of slag, the cost of washing, smelting and
refining, wages, tools, charcoal and wood fuel all included, amount to
fl. 27 to fl. 30 per pikul of tin produced.
The refining of residual and slag tin, as far as the first liquation is
concerned, costs per pikul of tin 25 to 30 cents, in wages, wood for
fuel, and sundries, as already stated. The marketable tin obtained
from the liquation tailings costs fl. 4 to fl. 5 per pikul for refining.
( 296 )
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tin occurs both in recent gravels and in old channels covered by basalt
flows ; lodes from which the Yegetable Creek tin has been derived ;
average thickness, extent, and richness of the alluvial deposits.
BIBLIOGRAPHY. 297
Derrick (W. H.). Notes on Lode Mining in the Malay Peninsula. Paper
read before Institution of Mining and Metallurgy, 9th October, 1898.
Emmons (S. F.). Geological Distribution of the Useful Metals in the
United States : Trans. Am. Inst. Min. Eng., Yol. 22, 1893, pp. 71, 72.
Describes the geologic occurrence of tin in various parts of the
United States.
Fairbanks (H. W.). The Tin Deposits at Temescal, Southern California :
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Yol. 75, 1897, p.. 362.
Describes the geologic features of the region and the occurrence of
the vein system and the tin deposits.
Fawns (Sydney). Notes on the Mount Bischoff Tin Mine. Paper read
before the Institution of Mining and Metallurgy, 1904.
Frecheville (R. J.). Great Main Lode of Dolcoath : Trans. Royal Geol.
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Relation of tin lodes to older dykes ; vein minerals — tourmaline,
quartz, and mica ; depth of workings ; physical character of the rich
tin ore ; passing of tin ore into the granite wall ; average richness of
tin ore from a number of Cornish mines.
Flett (John S.) :
Notes on some Brecciated Stanniferous Yein Stones from Cornwall.
Published in Memoirs of the Geological Survey of the United Kingdom,
1903.
Preliminary Notes on the Petrography of Cornwall. Published in
the Summary of Progress of the Geological Survey of the United
Kingdom, 1904.
Halse (Edward). The Occurrence of Tin Ore at Sain Alto, Zacatecas,
with reference to similar deposits in San Luis, Potosi, and Durango,
Mexico : Trans. Am. Inst. Min. Eng., Yol. 29, 1900, pp. 502-511,
Figs. 1-6.
Describes the occurrence of the various ore bodies.
Hanks (H. G.). Cassiterite : Fourth Annual Report of the State Mineral-
ogist of California, 1884, pp. 115-123. Notes on Tin Ores from
Temescal, Cal.
Hen wood (W. J.). On the Metalliferous Deposits of Cornwall. Trans.
Roy. Geol. Soc. of Cornwall, Yol. 5, 1839.
HOFMAN (H. O.). Dry Assay of Tin Ore : Trans. Inst. Min. Eng., Yol. 18,
1890, pp. 3-54.
Describes an exhaustive series of experiments with the ores of the
Black Hills to ascertain the best method of assaying tin ores.
Ingalls (W. R.). The Tin Deposits of Durango, Mexico : Trans. Am.
Inst. Min. Eng., Yol. 25, 1896, pp. 146-163.
Presents a map of a portion of Mexico, showing the location of
the tin-ore deposits ; describes the general geologic features, and
the character and description of the ore bodies, and discusses their
origin.
Kayser & Provis. Mount Bischoff Tin Mine, Tasmania. A paper pub-
lished by the Institution of Civil Engineers, Yol. 123, Part I.,
Session 1895-6.
298 TIN DEPOSITS OP THE WORLD.
Kempton (C. W.). The Tin Deposits of Durango, Mexico : Trans. Am.
Inst. Min. Eng., Yol. 25, 1896, pp. 997, 998.
In discussion of Paper on the same subject, by W. R. Ingalls; men-
tions an occurrence of tin placers at Sain Alto, Zacatecas, Mexico.
Louis (Henry) :
Metallurgy of Tin : The Mineral Industry, Yol. 5, 1896, pp. 5?.3-
588.
Methods of smelting tin ; character of furnace lining, etc. Three
stages in tin smelting: (1) reduction ; (2) refining impure tin; (3)
cleaning the slags.
Production of Tin. Reprint of series of articles in the Min. Jour.,
Railway and Commercial Gazette, 12mo., 39 pp. and map. London, 1900.
MacAlister (D. a.) :
A Cross Section and some Notes on the Tin Deposits of Camborne,
Cornwall. Paper read before the Royal Geological Society of Corn-
wall, 1903.
Yertical Distribution of the Commercially Yaluable Ores in the
Camborne Lodes. Geological Survey, 1903.
MacAlister (D. A.) and Hill (B. J.)
The geology of Falmouth and Truro, and the Mining District
of Camborne and Redruth. An exhaustive treatise on the geology
and ore deposits of the region from a scientific and economic point of
view. The subjects treated comprise the origin and distribution
of the ores, together with detailed accounts of individual mines. A
description of ore dressing processes as practised in Camborne is
followed by complete statistical tables of the output of tin, copper and
other minerals.
Mackenzie (S. L.). Determination of Tin in Tailings. Paper read before
Institution of Mining and Metallurgy, 19th November, 1903.
Maitland (A. Gibb). The Mineral Wealth of West Australia. Tin
pp. 84-90. Published by Geological Survey, 1900.
MiNCHiN (J. B.). Tin in Bolivia : The Mineral Industry, Yol. 2, 1902,
pp. 588-590.
Description of tin-producing district and tin-bearing lodes ; methods
of mining, transporting, and concentrating tin ores.
MoissENET (L.). Observations on the Rich Parts of the Lodes of Corn-
wall. Their form and their relations with the Directions of the
Stratigraphic Systems ; translated from French, by J. H. Collins, 1877.
Owen (Frank). Mining in Perak.
Account of deposits and mining in Perak, describing methods
of Chinese workings ; tin buying ; Chinese assaying ; method of
tributing hydraulic mining ; various tables of working cost ; Chinese
tin smelting. Inst, of Min. and Met., London, Yol. 6, pp. 51-87,
17th November, 1897.
Owens (F.). A Review of the Tin Industries of the Malay Peninsula up
to the end of 1899 : The Mineral Industry, Yol. 9, 1901, pp. 646-656.
Parry (L.). Assay of Tin and Antimony.
Full description of the various methods of tin assaying. 1904.
Pasley (Chas. S.). Tin Mines of Bolivia. A Paper read before the In-
stitution of Mining and Metallurgy on the various tin mines and
methods of working them in Bolivia. 1903.
BIBLIOGRAPHY. 299
Penrose (R. A. F.). Tin Deposits of the Malay Peninsula : Jour. GeoL,
Vol. 11, 1903, pp. 135-154.
Geology of the Kinta district ; description of tin placers ; methods
of mining and treating tin ores.
Phillips (J. A.) and Louis (Henry). Treatise on Ore Deposits :
Macmillan & Co., London, 1896.
Description of both alluvial and lode deposits of tin in various parts
of the world, and discussion of the genesis of tin ore.
Phillips (William). On the Veins of Cornwall, and Oxide of Tin :
Trans. Geol. Soc, London, Vol. 2, 1814, pp. 336-376.
PiTTMAN (Ed. F.). Tin Deposits of New South Wales. Published by the
Government, giving a full description of the mines, and methods of
working. 1899.
Prosepey (Franz). The Genesis of Ore Deposits. The genesis of tin ore
deposits discussed at length, with discussion on same. Published by
the American Institution of Mining Engineers, 1902.
ROLKER (C. M.) : .
The Alluvial Tin Deposits of Siak, Sumatra : Trans. Am. Inst.
Min. Eng., Vol. 20, 1892, pp. 50-84. Notes on the geology and the
occurrence and methods of working tin-bearing gravels.
The Production of Tin in Various Parts of the World : Sixteenth
Ann. Report U. S. Geol. Survey, Pt. 3, 1895, pp. 458-538. Includes
statistics of production in various countries, and notes on the occurrence
of tin in Maine, Virginia, North Carolina, Alabama, Texas, South
Dakota and California.
Saunders (W. T.). Tin Mining in the Straits Settlements. A Paper read
before the Institution of Mining Engineers, 1904.
Thomas (R. Arthur). On Crushing and Concentration at Dolcoath Mine,
Cornwall. Paper read before Institution of Mining and Metallurgy,
giving a description of the machinery and methods of tin dressing at
Dolcoath, 15th March, 1899.
TWELVETREES (W. H.) :
Government Geologist to Tasmanian Governments. Report on the
Deep head or infra basaltic stanniferous gravels of the Ringarrooma
Valley near Derby.
Report on the Anchor Tin Mine and other mines of the Blue Tier
District, Tasmania, published by the Mines Department of Tasmania ;
and other reports by W. H. Twelvetrees, years 1900 to 1904.
TwELVETREES & Pettered. On the Topaz Quartz Porphyry or Stanni-
ferous Dykes of Mt. Bischoff. Paper read before the Royal Society
of Tasmania, 11th October, 1897. Giving a description of the results
of microscopic determination of the Mount Bischoif rocks.
Ulke (Titus):
A Contribution to the Geology of the Dakota Tin Mines : Eng. and
Min. Jour., Vol. 53, 1892, p. 547. Includes a brief description of the
archaean rocks in which tin occurs; the mineral species found ; and a
discussion as to the origin of the tin-bearing granites.
The Occurrence of Tin Ore at King's Mountain, North Carolina,
and near Vesuvius, Virginia : Mineral Resources, U.S., for 1893; U.S.
Geol. Survey, 1894, pp. 178-182. Describes the character of the
country rock of the two localities and the manner of occurrence of the
tin ore.
300 TIN DEPOSITS OF THE WORLD.
Waller (G. A.) and Hogg (E. G.)- On the Tourmaline Bearing Rocks
of the Hennskirk District, published in the report of the Secretary of
Mines for Tasmania, 1902-1903.
Weed (W. H.). The El Paso Tin Deposits : Bull. U.S. Geol. Survey,
No. 178, 1891. Description of occurrence of cassiterite in Texas.
Wood (J. E. Tennison) :
Report on the Great Western Tin Deposits, Herberton. 1881.
Report to the Government of South Australia on Tin Deposits of
Northern Territory, 1886.
( 301 )
INDEX.
Aberfoil River (N.S.W.), 1.
Abicaya (Bolivia), 127, 128.
Agricola and Ercker, Early History Tin
Mining, 6.
Alaska (U.S.A.), Deposits of, 178-183.
Alluvial Deposits, Description of, 18-20.
„ Deposits Banca, Billiton, Siak, &c.,
38-53.
„ Tin Mining, 54-64.
„ Deposits of Malay Peninsula,
21-37.
Altenberg (Saxony), 166-169.
Analysis of Tin, 6-7.
„ Northern Nigeria, 154-156.
„ West Australia, 108.
„ of Dr. Pollard, 172.
Anchor Tin Mine, 103-106.
„ „ „ Geology of, 103.
„ „ „ Method of Working, 104.
,, „ „ Description of Plant,
106.
Arksut (Greenland), 163.
Arnoyaseco (Spain), 169, 170.
Assay of Tin Ore, 233-250.
Avoca (Tasmania), 109, 110.
B.
Bailey's Mine (N.S.W.), 83, 84.
Banca, Deposits of, 38-41.
Bauchi (N. Nigeria), 154-156.
„ Geology of, 155.
„ Method of Working, 156.
Batu (Malay), 27.
Beiro (Portugal), 170.
Ben Lomond (Tasmania), 108, 109.
Bibliography, 296-300.
Billiton, 42, 43.
Blue Tier (Tasmania), 100, 101.
Bolivia, Tin Deposits of, 122-137.
„ Geology of, 122, 123.
„ Tin Statistics, 259.
Briseis Tin Mine, 111-113.
„ „ „ Method of Working,
112, 113.
British Burma, 46-52.
Brookstead (Tasmania), 110.
Brown Face (Mt. Bischoff), 185.
Buck Creek (Alaska), 178, 179.
Bucket Dredge, 228-231.
Buhner Creek (Alaska), 179.
Bundi Tin Mine (Malay), 69-73.
>» ,» }} Geology of, 70-72.
„ „ Glen Reef, 72.
Burra Burra (N.S.W.), ^^9.
Busanga Mine (Congo Free State), 161.
c.
Cacha (Malay), 27.
Cajalco Hill Mine (U.S.A.), 176.
Californian Stamps, Description of.204,206.
Camborne (Cornwall), 148, 149.
Campaglia Marittima (Italy), 171.
Cape Mountain (Alaska), 179, 180.
„ Colony, 159.
Carolinas Tin Belt (D.S.A.), 176.
Carbonas, 16, 17.
Cassiterides, 7, 8.
Cassiterite, 2, 3.
„ Creek (Alaska), 180, 181.
Gaunter Lodes, 12.
Caulfieldite, 4.
Cento Camerelle Mine (Italy), 171.
Central Europe, Deposits of, 166-169.
Centrifugal Pump Dredge, 227, 228.
Charleton, A. G., on Stock works, 167, 168.
Chaungtanaung (Burma), 47.
Chem. and Met. Soc. of S. Africa, 159.
China, Deposits of, 163-164.
Chinese System of Mining, 24-37.
„ Methods of Tin Smelting, 272-274
Chongkat Pari (Malay), 27.
Clark, D., on Mt. Bischoff, 192, 193.
Classification of Tin Deposits, 9-20.
Clitters Tin Mine, 211-214.
Clough,C.,on Scotch Tin Deposits,171,172.
Collier, A. J., on Alaska, 178-183.
Collins, J. H., on Dolcoath T. M., 196, 197.
„ „ Forms of Tin, 19.
„ „ Assay of Tin, 247.
Colorado (U.S.A.), 176.
Colquiri (Bolivia), 125, 126.
Common Forms of Stanniferous Minerals,
1-6.
Concave Buddie, 207.
Congo Free State Deposits, 160-162.
302
INDEX.
Connecticut (U.S.A.), 176.
Consumption of Tin, Table of, 257.
Contact Deposits, 14, 15.
Cook's Kitchen Mine (Cornwall), 149.
Cope's Creek (N.S.W.), 78, 79.
Cornish Stamps, Description of, 204.
Cornwall, Deposits of, 138-153.
Croix, De la, on Malay Deposits, 26.
Crystal HiU Mine (Tasmania), 103.
Cyanide Assay for Tin, 240, 241.
Cylindrite, 4.
D.
Dalmer, K., on Stock works, 15, 16.
Deep Leads (Malay), 27-33.
Derrick, W. H., on Pahang Corporation,
65-67.
Description of Tin Deposits, 9-20.
Diest, P. van, on Banca, 38-41.
Doeren (Banca), 40, 41.
Dolcoath Tin Mine (Cornwall), 194-203.
„ „ „ Tables of Results, 199.
„ „ „ Dressing Machinery,
199-203.
„ Main Lode, 194-196.
„ Series of Lodes, 141-144.
Dora Dora (N.S.W.), 89.
Double Treatment with Vanner8,218, 219.
Doyle, P., on Malay, 18.
Dredges, Method of Working, 230-232.
„ Description of Bucket Type,
229.
Dredging for Tin, 223-232.
Durango (Mexico), 173.
Duty of Water, 56, 57.
Dykes, Description of, 12-15.
E.
Early History of Tin Mining, 6-8.
Elevator for Dredges, 229, 230.
Elsmore Valley Lead, SO.
Embabaan (Swazieland), 160.
Emmaville (N.S.W.), 82, 83.
Enkeldoorn (Transvaal), 157, 158.
Euriowie Tin Field (N.S.W.), 89, 90.
Evans Slime Table, 208.
Extraction of Tin from Dross, 249.
F.
Federated Malay States, 21, 22.
Finland, Deposits of, 163.
Fircks, von, on Mt. Bischoff, 185.
Fissure Deposits, 9-12.
Flett, J. S., on Tin Veins, 11, 12.
France, Deposits of, 170, 171.
Franckeite, 3, 4.
Frecheville, R. J., on Dolcoath, 194-197.
G.
Gajah (Malay), 27.
Geological Survey of India, 47, 48.
GilfiUan and Cox on Burma, 47-52.
Golden Stream District, 49-51.
Gopeng (Malay), 27.
Glen Innes Division, 91.
Graveyard Lead (N.S.W.), 82.
Great Condurrow Series, 149.
„ Flat Lode Series, 146, 149.
„ Wheal Fortune, 15.
Greenbushes Tin Field, 115-118.
„ Geology of, 116, 117.
„ Tin Exported, 117.
Greenland Deposits, 163.
Griffiths, H. D., on Transvaal Deposits,
156-159.
Groddeck, von, on Mt. Bischoff, 185.
Groot, M. De, on Banca, 41, 42.
H.
Headings, Value of Tin in, 220-222.
Kenwood, W. J., on Lodes, 10-12, 16,
267.
Herberton (Queensland), 92-95.
„ Geology of, 92, 93.
„ Description of Mining, 94, 95.
Hill, J.B., on Lodes, 12, 147.
Hopper Box, Description of, 54.
Huanuni Hill (Bolivia), 123, 124.
Huntington Mills, 205.
Hydraulic Jet Elevator, 189.
„ Mining, Malay, 30.
„ Monitor, 61.
I.
Impregnations, Tin, 16, 17.
Inverell, 91.
Ipoh (Malay), 27.
Ireland, Deposits of, 172.
Italy, „ 171.
Japan, Deposits of, 162-163.
Jigger, 205.
Jingellic Lodes (N.S.W.), 87, 88, 89.
Johor (Malay), 21.
Jour. Geo. Soc, 2, 19, 143.
K.
Kampar (Malay), 27.
Kangaroo Hills (Queensland), 96, 97.
Kasonso, 162.
Kemaman (Malay), 69.
Kinta (Malay), 26-30.
Korea, Deposits of, 164.
JNDEX.
303
Kota Mines (Malay), 32, 33.
Kotta Rannah-Bambai (Sumatra), 44, 45.
Kuala Lumpur (Malay), 27.
Kuils River Tin Mine, 159.
La Paz, Bolivia, 128, 129.
Lahat (Malay), 27.
Lalang (Malay), 27.
Launcelot Mine (Queensland), 94.
Leh Chin Mine (Malay), 58, 59.
Levant Mine (Cornwall), 150.
Lodes, Description of, 9-12.
Louis, Henry, on Tin Deposits, 8, 164,
166,170.
M.
MacAlister, D. A., on Cornish Tin De-
posits, 139-149.
MacEenzie, G.L., on Tin A88aying,24 3,244.
Main Lode, Dolcoath, 194-196.
Malay States Statistics, 260, 261.
Market Price of Tin for 57 \ ears, 268.
Masses, Description of, 9, 15, 16.
Mergui District (Burma), 48.
Metallic Tin, 5, 6.
Metallurgical Processes, 280-286.
Methods of Tin Assaying, 233-250.
Mexico, Deposits of, 172-175.
Mineral Industry, 134, 135.
Minerals occurring with Tin, 5.
Mitta Mitta (Victoria), 121.
Moroeocala (Bolivia"), 124.
Mount Bischoff (Tasmania), 184-193.
,, „ Geology of, 186, 186.
„ „ Machinery at, 187-191.
„ Wells (Victoria), 121.
„ Rex (Tasmania), 109.
„ Wells (N. Territory), 119, 120.
Moving Power of Water, 57.
N.
Native Tin, 1, 2.
Negri Sembilan (Malay), 21.
Negro Pabellon (Bolivia), 125.
Nerius, J. N., on Mexico, 174, 175.
Nerchinsk (Siberia), 164.
New South Wales, Deposits of, 77-91.
„ „ Statistics of, 262.
New Zealand, Statistics of, 121.
Newstead Lead (N.S.W.), bO.
Nicolaus, R. C, on N. Nigeria, 154-156.
Northern Nigeria Deposits, 154-156.
,, Territory Deposit?, 119, 120.
0.
Oruro Mines (Bolivia), 123.
Ottery Tin Lodes (N.S.W.), 85, 86.
Padang Rengas Valley (Malay), 31.
Pahang Corporation (Malay), 65-69.
„ „ Plant, 68.
„ „ Working costs, 68, 69.
„ Deposits of, 65-69.
„ Kabang, 69.
Papan (Malay), 27.
Parry, L., on Assaying, 235-239.
Pearce, R., on Vanning, 233, 234.
Penrose, R. A. F., on Kinta, 26-31.
Perak, Deposits of, 21, 27-32.
Pitkaranta (Finland), 163.
Pitriac (France), 170.
Pneumatic Stamps, 205.
Portugal, Deposits of, 170.
Potosi (Bolivia), 131.
Production of Tin, 251-267.
Puket Island (Siam), 46.
Pumping Methods (Malay), 60.
Pyriac (France), 171.
Q.
Queen Lode, Mt. Bischoff, 185.
Queensland Tin Depos.ts, 92-98.
„ Statistics, 263.
R.
Raymond, R. W., on Deposits (U.S.A.),
177.
Refining Tin, Banca, 288-294.
Reverberatory Furnace, Description of —
In Cornwall, 269, 270.
„ Pulo Brani, 276, 277.
„ Tasmania, 271, 272.
Rookabookra (N.S.W.), 91.
Rose Valley, 82.
s.
Sain Alto (Mexico), 174, 175.
Sambong-giri (Bauca), 41.
Scotland, Deposits of, 171, 172.
Scrivenor, J. B., on Malay Tin Deposits,
74-76.
Selangor (Malay), 21.
SeUing Tin Ore, Cornwall, 271.
Shallow Alluvial (Malay), 22.
Siak (Sumatra), 44, 45.
Siam, Deposits of, 45, 46.
Siberia „ 164, 165.
Singkep, Island of, 43.
Single Treatment with Vanners, 219.
Sluice Box, Description of, 54.
Sluicing, Methods of, 54-56.
Smelting Costs, Banca, 295.
„ „ Tasmania. 272.
304
INDEX,
South Crofty Series, 148.
Spain, Deposits of, 169, 170.
Stannary Hills (Queensland), 96.
Stanniferous Argyrodite, 4.
Stannite, 1, 2.
Statistics of Tin Production, 251-268.
Stephens, F. J,, on Malay Minerals, 65, 66.
Stock-works, Description of, 15, 16.
Stokesite, 4, 5.
Suction Dredge, 227.
Sungei Ayam (Malay), 73.
,, Lembing „ 66.
Ralau Tujoh (Malay), 34.
Surface Alluvial (Malay), 22.
Swazieland, Deposits of, 159, 160.
T.
Tanganyika Concessions (Congo Free
State), 160-162.
Taniyama (Japan), 162.
Taiping (Malay), 74-76.
Tasmania, Deposits of, 99-114.
„ Statistics of, 261.
Taylor, J. W., on Greenland, 163.
Teallite, 4.
Tenasserim River (Burma), 48.
Thureau's Deep Lead (Tasmania), 113.
Tin Crushing and Dressing Machinery,
204-222.
Tingha, 91.
Tin Lodes (Malay Peninsula), 65-76.
Tin Smelting, 269-295.
„ „ Cornwall, 269-272.
,. ,. Singapore, 274-286.
„ „ Banca, 286-295.
Transvaal, Deposits of, 156-159.
Geology of, 157.
,, Alluvial Deposits, 158.
Trans. Am. Inst. Min. Bng., 27, 43, 148.
Trans. Inst. Civil Eng., 187-190.
„ „ of Min. and Met., 6, 7, 23,
199-203.
Trans. Royal Geo. Soc. of Cornwall, 3, 19,
138, 139, 143.
Treatment of Tjn Ore, 211-222.
„ „ Scrap Tin, 249.
Tringganu (Malay), 69-73.
Twelvetrees,W. H., on Tasmania, 101-103.
u.
United Kingdom Tin Production, 263.
,, States of America, Deposits of,
175-178.
Vegetable Creek (N.S.W.), 82.
Victoria, Deposits of, 120, 121.
Vilacollo (Bolivia), 124, 125.
Volumetric Estimation with Ferric Chlo-
ride, 237-239.
Volumetric Estimation with Iodine, 239.
Vulcan Mine (Queensland), 93.
w.
Waverley Mine (Queensland), 98.
Wellington Vale Lead (N.S.W.), 82.
Western Australia, Deposits of , 115-119.
„ „ Statistics, 262.
Wet Assay of Tin, 247.
Wilfley Table, 206.
Wood, Tennison, on Tin Deposits, 33.
„ Tin, 3.
Working Deep Leads, 60.
Yamon (Burma), 47.
Zinnwald (Saxony), 168.
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me
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Mipifflflm Workip^ Costs, Power CoDsnmption, and wear & tear.
Maxifflam Capacity and EMciency on all kinds of material.
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Estimates on Mining, Milling and Treatment Plants furnished,
Designs for Single Units or Complete Plants prepared, and Con-
tracts entered into for supply of the Entire Outfit, including buildings
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